The answer to your question is A. - Them because you are referring to the crumbs and just not something random, in which case you would use "it".
I hope this helps you!
Have a great day!!
What I do is I put in my earbuds and listen to music. It helps me and I don't go off task. If that doesn't help then try setting an alarm on your phone for 30 minutes read till that alarm goes off then take a 5 or 10 minute break then go back to reading for another 30 minutes. Hope this helps :)
