Plz will upvote

what is the second most abundant element in stars?
a.
helium

b.
hydrogen

c.
iron

d.
oxygen

Clyde and marilyn are riding a roller coaster. during which section(s) of the track is their potential energy converted to kinetic energy? a. from point b to point c only b. from point b to point d only c. from point a to point b only d. from point a to point b and from point c to point d