____ (30) _____, a significant minority of people still do it, despite the sighing and other obvious signs of disapproval from their fellow passengers.

The answer is NO

Knowledge: Conjunctions

Therefore, S + V : Therefore, Therefore,… => only result

However, S + V : However => indicates contrast

Moreover, S + V : In addition, in addition, more than that

Otherwise, S + V: Otherwise

Talking loudly on the phone while on public transport is thought to be rude and inconsiderate by many people in the UK. … => talking loudly in public is rude and inattentive

(30) Howevera significant minority of people still do it,…

However, a very significant number still do it…