I believe it is d, a microhabitat is a small area which differs somehow from the surrounding habitat. Its unique conditions may be home to unique species that may not be found in the larger region.
Molar volume is when 1 mol of any gas occupies 22.4 L at STP.
Methyl ether has a mass of 8.12 g,
Volume occupied - 3.96 L
If 22.4 L occupied by 1 mol of gas
Then 3.96 L occupied by 1/22.4 x 3.96 = 0.176 mol of gas
The mass of 0.176 mol = 8.12 g
Molar mass is mass of 1 mol
Therefore mass of 1 mol = 8.12/0.176 = 46.1
Molecular weight is 46.1 g/mol