From Twitter:

1. A: Please __ all the way in, so the rude, inconsiderate people pushing to get in--crushing us like farm animals--can stop that.
   B: Huh?
   2. A: Please __ as far as you can--in, so others may enter too.
   B: We don't mind.
   A: We do.
   
   Choose:
   a. go
   b. step
   c. set foot
   d. tread

Answers and Explanations
1. b., step meaning to walk--by putting one foot forward after another and is used with 'into' (or with 'in,' 'on,' 'over,' and 'around.'
2. a., go meaning to proceed or continue moving.