Which position for hydrogen explains all its properties?

When $NaBH_4$ is dissolved in water,

$TiH_{1.73}$ is an example of

Given below are two statements: one is labelled as Assertion $(A)$ and the other is labelled as Reason $(R).$
Assertion $(A):$ Heavy water is used for the study of reaction mechanism.
Reason $(R):$ The rate of reaction for the cleavage of $O-H$ bond is slower than that of $O-D$ bond.
Choose the most appropriate answer from the options given below:

The hydrides of which group elements are examples of electron-precise hydrides?

Hydrogen readily combines with non-metals and thus it shows its