次は推量の確信度の高い方から順番に書かれた文です。 では、He will be having a meeting with his client.は(1)(2)のどちらに入るでしょう?
He must be having a meeting with his client.(会議中にちがいない) ↓(1) He should be having a meeting with his client.(会議中のはずだ) ↓(2) He may be having a meeting with his client.(会議中かもしれない)