When an acid reacts with a metal it results in the formation of salt and hydrogen gas is liberated. For example, the nitric acid reacts with the calcium it forms salts of calcium nitrate and hydrogen gas is liberated.
Genetic engineering is applied to techniques like DNA cloning in which the steps are: step 1: DNA cutting from the parent source; step 2: DNA cut is pasted into the matrix to be modified; step 3: matrix is introduced to the host cell and step 4, vector DNA is isolated. Answer then is B.