Choose the word most nearly antonymous (opposite in meaning) to the capitalized word:
SYNTHETIC
Synthetic means made by chemical processes rather than occurring in nature, so it means man-made or artificial. The opposite is something that occurs on its own in nature, which is natural.
The opposite of man-made is natural, so the answer is natural.
If the price of a commodity increases by 25%, by what percentage should the consumption be reduced to keep the expenditure the same?