Question

1.I can't find my bicycle. I think someone (steal) it.

2. Tom isn't here. He (go) to work.

Answer 1

1.I can't find my bicycle. I think someone (steal)stole it.

2. Tom isn't here. He (go)has gone to work.

Answer 2

1.I can't find my bicycle. I think someone (could have stolen) it.

2. Tom isn't here. He (must have gone) to work.

Answer 3

1. has stolen

2. must have gone.