Answer:
A. 336 L
Explanation:
STP is 0 °C and 1 bar.
At STP, the molar volume of a gas is 22.71 L.
Volume = 15 mol × 22.71 L/mol
Volume = 341 L
===============
The above answer is not in your list of options.
It appears that you are using the OLD (pre-1982) definition of STP, at which the molar volume of a gas is 22.4 L.
Then
V = 15 mol × 22.4 L/mol = 336 L
