In the following passage, some of the words / sentences have been left out,…
2024
In the following passage, some of the words / sentences have been left out, each of which is indicated by a number. Find the suitable word / sentence from the options given against each number and fill up the blanks with appropriate words / sentences to make the paragraph meaningful.
The layer of ozone helps _____ 1 _____ the harmful ultraviolet rays away from entering the Earth’s atmosphere. Ozone layer depletion over the years has _____ 2 _____ in ozone hole formation through which harmful radiations can now enter the atmosphere. Ozone layer depletion has many _____ 3 _____ effects including cancer risks. These wavelengths can harm plants and animals and also cause skin cancer, sunburn, and cataracts in humans. The problem is very _____ 4 _____ indeed and has rightly generated global concern. These concerns led to the _____ 5 _____ of the Montreal Protocol in the year 1987. This protocol bans the production of ozone-depleting chemicals like CFCs and halons. Ozone depletion refers to a steady _____ 6 _____ in the total amount of ozone present in the Earth’s atmosphere or the ozone layer. It can also be described as a much larger decrease in stratospheric ozone around the polar regions of the Earth. The second phenomenon is termed as the ozone hole. In addition to these stratospheric events, there are also springtime polar tropospheric ozone depletion events. _____ 7 _____ . These compounds enter the stratosphere after being emitted at the surface where these compounds release halogen atoms by a process called photo dissociation. _____ 8 _____ . The main cause of ozone layer depletion is the indiscriminate use of CFCs, which are chlorine-based substances. These are widely used in several manufacturing plants, refrigerants and aerosols. _____ 9 _____ . Just one atom of chlorine can destroy around 100, 000 molecules of ozone. Wind blows the CFCs up into the stratosphere. Ozone molecules are already unstable. The chlorine atoms in the CFCs react with the ozone molecules, which break down resulting in the formation of an oxygen molecule and a single free-floating oxygen atom. _____ 10 _____ . However, chlorine in other places such as swimming pools does not pose any danger.
Find the appropriate word / sentence for blank 10.
(question no 6 till 15 are linked together)
- A.
It should be kept in mind that chlorine molecules should not be left unattended anywhere without any solvent being attached to it.
- B.
Utility of any solvent is known when the same is used for everyday purposes and not only for chemical reactions.
- C.
The chlorine is a powerful solvent and it should be noted that it is a very reactive one also.
- D.
The chlorine in the atmosphere has immense threat potential.
Attempted by 3 students.
Show answer & explanation
Correct answer: D
In a cloze / passage-completion item, the sentence chosen to fill a blank must keep the passage's logical flow intact — it has to connect smoothly with both the sentence immediately before it and the sentence immediately after it (as a cause-effect link, a connector, or a contrast). A sentence that merely reuses similar vocabulary but does not carry this connecting logic breaks the flow even though it looks topically related.
The sentence right before this blank describes how a chlorine atom breaks down an ozone molecule in the atmosphere, forming an oxygen molecule and a free oxygen atom — a destructive reaction. The sentence right after the blank opens with “However, chlorine in other places such as swimming pools does not pose any danger,” which is a contrast that only makes sense if the blank first states that chlorine in the atmosphere IS dangerous. The option that says the chlorine in the atmosphere has immense threat potential supplies exactly this statement, so it slots in and sets up the following contrast.
Reading the passage with this sentence inserted gives a coherent chain: chlorine destroys ozone molecules in the atmosphere → atmospheric chlorine is therefore a serious threat → however, chlorine elsewhere (swimming pools) is not a threat. None of the other sentences, when substituted, produce this coherent before-blank / after-blank link — each of them talks about chlorine or solvents in a way that is disconnected from the swimming-pool contrast that follows.
“Chlorine molecules should not be left unattended anywhere without any solvent being attached to it” is about handling/storage practice, not about atmospheric danger, so it gives the following “however” nothing to contrast against.
“Utility of any solvent is known when the same is used for everyday purposes” is a generic remark about solvents in general and never mentions chlorine's danger in the atmosphere.
“The chlorine is a powerful solvent and ... a very reactive one” only describes a chemical property of chlorine as a solvent, without asserting any atmospheric threat for the contrast to work against.