1.  sustenance
A. nourishment
B. water
C. grains
D. menu

Answer: Option A

Explanation:

Sustenance is something, especially food, that sustains life or health, so nourishment is the essential element.Water and grains (choices b and c) are components of nourishment, but other things can be taken in as well. A menu (choice d) may present a list of foods, but it is not essential to sustenance.