I think I found it. The answer must be the second one. The reason is: Although 'When I arrive tomorrow' seems present tense, it is not. Normally, it means 'I though someone would wait for me when I would arrive tomorrow'. But we can't use 'would-will' after 'when'. For this reason the answer must be:
-I thought someone would wait for me when I arrive tomorrow.
But how about it?
I think I can do my homework before my father is here tomorrow.
-I thought I could do my homework before my father be/was here tomorrow.
Which one must we use?