Select the most appropriate ANTONYM of the underlined word in the given…

An antonym is a word whose meaning is directly opposite to another word’s meaning. To find it, first fix the precise sense of the underlined word as used in the sentence, then choose the option whose meaning stands in direct contrast to that sense — not a synonym, and not an unrelated attribute entirely.

Here, "turbid" describes a liquid that is cloudy, murky, or opaque because it is thick with suspended sediment — it lacks transparency. The word that names the directly contrasting state, a liquid that is transparent and free of suspended matter, is "Clear".

Checking each option against this contrast:

• Muddy — restates the same cloudy, sediment-laden quality as turbid, rather than opposing it.

• Deep — refers to vertical extent, how far down the water goes, a dimension unrelated to transparency.

• Fresh — refers to salinity or how recently the water was drawn, again unrelated to transparency.

Hence, the word denoting the contrasting, transparent state, Clear, is the correct antonym.