Answer
(a) 4
(b) 8
(c) 6
(d) 12
Work Step by Step
(a) In CH$_4$, we can count 4 atoms of hydrogen.
(b) In C$_3$H$_8$, we can count 8 atoms of hydrogen.
(c) In C$_6$H$_6$, we can count 6 atoms of hydrogen.
(d) In C$_6$H$_{12}$O$_6$, we can count 12 atoms of hydrogen.