How can you to prevent muscle mass loss as you age?
a. maintain a regular exercise program.
b. cut back on the amount of calories you eat during the day.
c. lift weights twice a week.
d. you can't prevent muscle mass loss; it's inevitable as you get older.

c is having 4 valence electrons and is bonded to three hydrogens and one sulphur atom, therefore, the number of bond pair is equal to four. as all the valence electrons are used in forming the bonds so, there is no lone pair left on carbon.

s is having 6 valence electrons and is bonded to one other sulfur atom and one carbon atom, therefore, the number of bond pair is equal to 2. as only two valence electrons are used in forming the bonds so, four electrons are left. therefore, two lone pairs are present on s.