The Symbols +, −, and 0 Are to Be Used

Multiple Choice

The symbols +, −, and 0 are to be used to show the results of interactions between individuals and groups of individuals in the examples that follow. The symbol + denotes a positive interaction, − denotes a negative interaction, and 0 denotes where individuals are not affected by interacting. The first symbol refers to the first organism mentioned.
-What interactions exist between a tick on a dog and the dog?

A) +/+
B) +/0
C) +/−
D) 0/0
E) −/−