Which sentence does not contain any errors in comma usage?
a. according to my mother, an inner tube, is the best way to be in the water.

b. if thunderclouds are rolling in, get out of the water.

c. oh look out, for that motorboat!

d. thinking about my afternoon plans i didn't notice the crashing wave until it was too late.

which sentence does not contain any errors in comma usage?

a.
breaking on the shore waves can, easily knock a swimmer over.

b.
gee i forgot to pack my surfboard.

c.
in shallow water, near the shore, beginning swimmers are usually safest.

d.
when we arrive at the beach each day, we check to see how rough the surf is.