What's the prepositional phrase in each sentence? each sentence contains one. the black car sped quietly through the woods. the medicine from the injection entered my bloodstream. are you going to the dance? i received a letter from my friend. the cup under the sink had grown cold. we grew sweaty in the heat.

Hey there!

A prepositional phrase is phrase that starts with a preposition and ends with noun (or a pronoun).
 Here is a list of a few prepositions:
About
above
across
after
along
among
around
at
before
beside
between
against
within
without 
beneath 
through
during
under
in
into
over
of
off
to
toward
up
on
near
for
from
except
by
with
behind
below
down
inside
until
outside

I know that was a long list but trust me, it will come in handy!

And a noun, as you should know, is a person, place or thing.

The preposition in the first sentence is 'through'. The phrase is 'through the woods'.

the second sentence is 'from the injection' because 'from' is a preposition, and 'injection' is a thing.

The third sentence is 'to the dance' because 'to' is a preposition and 'dance' is a place.

I won't give the rest of the answers because I want you to learn it, not cheat. Cheating doesn't get you anywhere. I cheated once as well and now I am a month behind in my homeschooling because I don't know the material.

I do not recommend cheating. :)