Which sentence uses a verb that agrees with its compound subject?
a. bill or rudy have called twice for tim.
b. either clara or her sisters has borrowed my scissors.
c. neither the umbrellas nor the tree protects us from the sun.
d. peggy and sydney is waiting for you.

The correct sentence is C. Neither the umbrellas nor the tree protects us from the sun.

In compound subject, the nearest subject form is the form used by the verb. In this case, tree is in singular form thus, the verb is in singular form.

Should be:
Bill or Rudy HAS called twice for Tim. 
Either Clara or her sisters HAVE borrowed my scissors.
Peggy and Sydney ARE waiting for you.