Word is followed by four explanatory expressions. Choose the expression which…

Concept: A kaleidoscope is, literally, an optical instrument that uses mirrors and loose pieces of colored glass or plastic to produce an endless variety of symmetrical patterns as it is rotated. English usage has extended the word figuratively to describe any situation, scene, or sequence made up of many different elements that keep changing — this figurative sense is what one-word-substitution questions test.

Application: Among the four expressions offered, "a situation containing different parts that keep on changing" directly restates this figurative meaning, so it is the expression that best describes 'kaleidoscope.'

• "a weapon used by the army to fire many shells at the same time" names a multi-barrel rocket launcher — a military term with no connection to a constantly changing pattern or scene.

• "a clock that gives time of various countries" names a world clock — a timekeeping device, not an expression about variety or change.

• "a telescope with different lenses" invokes an optical device but wrongly reduces kaleidoscope to a lens-based, distance-viewing instrument; a kaleidoscope's defining mechanism is mirrors and loose pieces producing change, not interchangeable lenses.

Conclusion: The expression that best describes 'kaleidoscope' is: a situation containing different parts that keep on changing.