Question

The suffixes -ed, -ful, -ing, and -y can be added to the end of the word taste.

For which of the following do you not need to drop the final e before adding the suffix?

Answer 1

Look at each of the words:
tasted
tasteful
tasteing
tastey

as you can see, the last two words should be spelled tasting and tasty, but the first two words are correct without dropping their e's.
So the answers are the suffixes
-ed and -ful