What is the meaning of the apostrophe in the following sentence? 
"My sisters' bikes are in the front yard."

It's the genitive 's' and the plural form of sister.

Can you place a comma (,) before a coordinating conjunction (and, but, nor, or)?

Only when it splits two independent clauses (ie: two complete sentences); When creating lists.

Which of these punctuation marks CANNOT come at the end of a sentence? ! ;  .

In British English, (   ) are called "round brackets", but in American English they're often called...

A) To join two related independent clauses in place of a comma and a coordinating conjunction

B) They are used between a dependent clause and an independent clause.

C) To replace a period between related sentences when the second sentence starts with either a conjunctive adverb/ transitional expressio

What is the meaning of the apostrophe in the following sentence? "My sisters' bikes are in the front yard."