What is it called when a line of poetry continues on to another line both in sense and in grammar?
a.
end-stopped
b.
alliteration
c.
enjambment
d.
assonance

It is called an enjambment (c)

This is used for effect in poems, if you didn't know already.
( you're smart so you probably do know, but idk if you do )

Here is an example of an enjambement: Far lands he goes past( enjambent)
in his day. The voyage is strange,
Fastening his ship's mast,
Going where discovering remained.

Your answer is C.  Enjambment.