1a. make the statemens more polite. example: tou're not right. (think) - i don't think (that) you're right. 1. it wasn't an explosion. (think) 2. they weren't humans. (believe) 3. james hasn't got an alibi. (think) 4. scientists can't explain their disappearance. (believe)

1. I don't think it was an explosion. 
2. I believe they weren't humans. 
3. I think that James hasn't got an alibi. 
4. I believe that scientists can explain their disappearance.