MSS questions will typically ask you to make a deduction about the argument/author without adding any information. The answers to Strengthening questions will introduce new information which when combined with the stimulus yields a stronger argument (the correct choice will at least). Its probably a good idea to review the MSS and STR curriculum if this isn't clear. Spend the time now and save it on test day.

What do we know about people who did not RSVP? We know they did not attend.

What do we know about people who did not attend? Nothing!

Think back to the sufficient and necessary rules. Based on how we know what we know, we can place the terms in the correct position.

This is a little unorthodox, but personally, it stops me from overthinking.

/RSVP->/Attend.

contrapositive = Attend->RSVP.

If you attended, you must have RSVP'd.

Lastly, because Rudy did not RSVP, we know he did not attend.

Does that help?

Seems to me that because neither piece can independently support the conclusion, there is only one premise. Try to remove one of the fragments and see if you still have questions.

For example on 3.1 -

For the public's complaints about the public transport systems have eroded confidence in such systems, the municipal body is bound to react.

I would still ask myself why the body would react. What motivates them?

Ex 2.

For these systems are vital to urban lifestyle, the municipal body is bound to react.

What systems?