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:

  one day samantha and her brother carson was walking in a path then samantha's brother carson almost stepped on something on the ground "carson, stop! " she shouted "huh, why? " he stopped "beacause, this" she says picking this mysterious object off of the ground it looked like a smart watch but there was another under it, one of them was gold one was silver. "woah, smart watches! " carson said "yeah, woah, you want gold or silver? " sam said "ummm, i'll take silver" carson smiled

  when they put it on it started to glow but no one was around, wafter 30 seconds of waiting a small silver dragon   came to carson, about the same time a golden lion came to samantha. "carson you need to get us some where safe so all of us can talk." the dragon said in his squeaky voice "by the way im silvester"   he said "we need to also samantha, im goldy." she said in her sqeaky voice.

  samantha and carson were suprised, scared and happy at the same time, so they took the little animals to their shed that nobody but them go into. "so where did you guys come from? " samantha said as they all sat down, "goldy and i, came from a far away land called zelda 101," silvester said "we are partners looking to find two human partners and you two are the perfect type, we could all be a team in zelda 101 and many other places that need certant things." goldy said "would you be willing? " silvester said

  "most definetly! " they both yelled "shh" silvester and goldy shouted. "ohh sorry" samantha and carson said.