Sorry if I'm wrong but I think that it is B.
Answer: 3.024 g grams of hydrogen are needed to convert 76 grams of chromium(III) oxide, 
Explanation:
The reaction equation for given reaction is as follows.

Here, 1 mole of
reacts with 3 moles of
.
As mass of chromium (III) oxide is given as 76 g and molar mass of chromium (III) oxide
is 152 g/mol.
Number of moles is the mass of substance divided by its molar mass. So, moles of
is calculated as follows.

Now, moles of
.given by 0.5 mol of
is calculated as follows.

As molar mass of
is 2.016 g/mol. Therefore, mass of
is calculated as follows.

Thus, we can conclude that 3.024 g grams of hydrogen are needed to convert 76 grams of chromium(III) oxide,
.
From the reduction standard potentials;
The emf of Zinc = -0.76 V
and the emf of Aluminium = -1.66 V
In a galvanic cell the component with lower standard reduction potential gets oxidized and that it is added to the anode compartment.
Therefore. the voltage of a galvanic cell made with zinc and aluminium will be;
Voltage =Ered- Eoxd
= -0.76 - (-1.66)
= 0.9 V