Riddle

Needed to jack, but also to carp. I can't be used in rust, but can in the grass. What am I?

Choose an answer

A.The letter R
B.The letter C
C.The letter K
D.The letter A
Hint: It's a 3-word phrase with 10 letters, starting with "T".

Answer

The letter A

Why this is the answer

"Jack" and "carp" both contain the letter A, "rust" does not contain an A, and "grass" does.

This riddle is filed under Hard/Difficult Riddles and rated Hard.