Judging by those answer choices provided above, it is safe to say a phone dialer is not needed so we can exclude that from the problem. A milestone is like a huge discovery, which does not make too much sense here. Which leaves us with two semi correct answers. Both C and D. A to do list would be great, but you would need to organize what you will do for the entire week before making a to do list, which leaves you with your best option!
~Hope this helps! I am, yours most sincerely Joshua A. Bunn
None of the words in this sentence should be followed by a colon. A colon is primarily used before listing certain things after a hard break in a sentence. Commas are fine here.
