In this sentence, the phrase "had been involved in the hit-and-run from last year" is not a subordinate clause. Rather, it is part of the main clause and helps to identify which truck in particular the speaker is referring to. Because it is not subordinate, the use of the word "which" is inappropriate and confusing. The word "that" should be used instead.

This sentence mixes up the words “that” and “which.” “Which” is used to start a phrase that provides additional information after a comma. The content of a which-phrase is loosely connected to the content of the main phrase, and the sentence would still make sense if the information contained in the phrase were omitted. “That” directly follows the word it’s modifying, with no comma intervening. The corrected sentence reads, "Nancy brought over the most heavenly-smelling batch of pecan rolls, which would have been lovely if I weren’t allergic to both nuts and gluten."

"It's" is the contraction, meaning "it is." "Its," without the apostrophe, is the possessive pronoun - the correct one that should be used here. This is a VERY common error, just remember that this is a rare case where the possessive form specifically does not take an apostrophe.

Although "you're" is correct the first time it appears in the sentence, it is a contraction of "you are;" it is, in other words, a subject and a verb. In the second half of the sentence, "happy days" is an object that the speaker is talking about, and "you're" should be changed to your, the possessive form of the pronoun "you." This makes it clear that she has happy days, but is not herself made of happy days. To see the problem more clearly, replace "you're" with "you are" every time it appears: "...I hope to multiply you are happy days..."

Here, the correct form of the present perfect is “wouldn’t have had to sleep,” not “wouldn’t have have to sleep.”

The form of the sentence requires that we use the past perfect (e.g. "I had done something") instead of the present perfect (e.g. "I have done something") since the speaker is discussing the time "before [he or she] began volunteering at the shelter." The correct form of the past perfect is “I’d,” a contraction of “I had," instead of "I've," a contraction of "I have."

Here, we have a simple verb error. The correct form is always “supposed to,” never “suppose to.”

We have another simple verb error here. Despite how it sounds in spoken dialogue, the correct form is always “wouldn’t have” and never “wouldn’t of.”

The phrase “can’t hardly” works as a double negative and is grammatically incorrect. If you can’t hardly see something, you can actually see it pretty well, which is clearly not the meaning that the speaker of this sentence intends. The correct form would be “I can hardly see the road.” Elsewhere in the sentence, the semicolon is the correct punctuation, since it’s separating two independent clauses.

Here we have another error with the present perfect. The correct conjugation is “they had driven,” not “they had drove.”