1. (Use the gerund trembling as a object of a preposition.)

A: My body perspires heavily instead of trembling.

2. (Use the gerund longing as a direct object.)

A: My longing makes my heart ache.

5 answers

1 is correct. 2 is not.

2. My longing has blinded me.

You haven't really changed this sentence. How have you used "longing" in each of them. And it's not a direct object.

http://www.chompchomp.com/terms/directobject.htm

2. I suppressed my longing by gorging myself with frozen yogurt.

Now you're right. :-)