6 Complete the text with past modal verbs speculation and the verbs given.

The person used the name Satoshi Nakamoto, so he (a) must have been Japanese. However, c are not so sure. They think that the person (b) might have used a Japanese pseudonym to confuse people found a man called Satoshi Nakamoto in Califor weren't sure but they thought he (c) could have been because he knew about computer pro 64-year-old Satoshi