1 I think it would depend on the context; I could take advantage of time if I used a few spare minutes to go outside for a cigarette, which wouldn't be making full use of it.
2 I can't see what's wrong with a). B) would be 'lost interest in' and d) doesn't really collocate for me.
3 'mutual interest' can exist for two people, but often carries the idea of reciprocating rather than sharing
4 It's much too dramatic for me; you'd make an unforgettable impression on someone if you walked into the room and set your hair on fire, but it probably wouldn't be favourable.
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