Question

1..when she was young she was very active in the field of social service (use modal auxiliary)
2.. if you wish, you are invited to join the group.(identify the clause )

Answer 1

1. she used to very active in the field of social service when she was young.
2. Main clause- if you wish
Sub-ordinate clause-you are invited to join the group

Answer 2

1)She used to be very active in the field of Sociai Science,when she was young.

2)Subordinate clause:Adverb of condition:If you wish.

Main clause:You are invited to join the group.