Which punctuation mark is missing from the following sentence?Since my best friend lives next door we get to see each other every day.

the comma after the word 'door.'

It's needed to separate the dependent clause from the independent clause. When the dependent clause precedes the independent clause, the dependent clause is ALWAYS followed by a comma. (<<<<  See? I just did it again in this sentence!)

Since my

best friend lives next door, we get to see each other every day.

Explanation:

- "the die is cast; i have consented to return if we are not destroyed. thus are my hopes blasted by cowardice and indecision; i come back ignorant and disappointed. it requires more philosophy than i possess to bear this injustice with patience. i have lost my hopes of utility and glory; i have lost my friend."