1. Be of + N

The constructor Be Of + Noun is virtually the same as Be + Adj except it sounds more formal. You can think of it as to be of a certain class or of a certain type. Among the best ~ Of the best Ex: The book is of interest Can I be of any help?

2. Was/Were + Doing

3. It vs That(This)

• both are pronoun

• IT: without nuance
• This/that: with nuance (emphasis), also repalce whole phrase/sentence

4. Progressive Aspect (Continuous Aspect)

• Emphasize the action last long, in a duration

• The action is in progress at the time of speak

• pass progressive: not normally do that, not a routine.

• temporary https://learnenglish.britishcouncil.org/english-grammar/continuous-aspect