Sentence 36: I should be able to fix your computer but I need some time to look ____the cause of the problem.
Explanation: look into (phrV): look into, study carefully
Remaining answers:
look round (phrV): look around, consider
look for (phrV): search
look about (phrV): wait
I can fix the computer for you but I need some time to find out the cause.
===============