Which word in the sentence is a plural pronoun?

we saw a few caterpillars crawling toward alex and her.

a.
her

b.
few

c.
caterpillars

d.
we

(First, I guess you chose the wrong subject since this is English not Physics :p)
Now, the pronouns are words that take the place of a noun.
The Personal pronouns are: I, you, he, she, it, we, they.
I, you, he, she, it are singular; while we and they are plural.
So, in the sentence, we can clearly see the pronoun "we", which is a plural pronoun.
So the plural pronoun in this sentence is We (Answer D)

Hope this Helps! :)

We is the plural pro noun

Neptune is the eighth planet from the sun. it was the first planet to get its existence predicted by  mathematical calculations  before it was actually seen through a telescope on sept. 23, 1846. irregularities in the orbit of  uranus  led french astronomer alexis bouvard to suggest that the gravitational pull from another celestial body might be responsible. german astronomer johann galle then relied on subsequent calculations to   spot neptune via telescope. previously, astronomer galileo galilei sketched the planet, but he mistook it for a star due to its slow motion. in accordance with all the other planets seen in the sky, this new world was given a name from greek and roman mythology — neptune, the roman god of the sea.