Answer:
Option B
Explanation:
Given that Calcium hydroxide and hydrogen gas are produced by the reaction of calcium hydride and water.
This gives that the two substances calcium hydride and water are the inputs and they react to produce the outputs Calcium hydroxide and hydrogen gas
Inputs must appear in the chemical equation on the left side and the outputs on the right side
Hence we get the correct answer to be one which has calcium hydride and water on left sid and Calcium hydroxide and hydrogen on the right side.
Out of 4 options only option B satisfies this fully
Hence
B.) calcium hydride + water → calcium hydroxide + hydrogen
is the right answer.