Answer: d. 97.99g/mol
Step-by-step explanation:
We need to add the molar mass of each of the atoms from the formula:
H3PO4 has 3x H atoms, 1x P atom, and 4x O atoms
H 3x 1.0079= 3.0237g/mol
P 1x 30.974= 30.974g/mol
O 4x 15.999= 63.996g/mol
now add all of the totals for each type of atom
3.0237 + 30.974 + 63.996= 97.9937g/mol
our answer is d. 97.99g/mol