Above the critical Mach number, a normal shock wave on the wing causes:

Reduced drag

A sudden increase in drag (drag divergence), boundary layer separation, and possible buffet

Correct

Increased lift without penalty

Smoother airflow

Explanation

Normal shock waves cause a sharp pressure rise, thickening and possibly separating the boundary layer, leading to wave drag and buffet.

Test yourself with random questions from Principles of Flight and all other ATPL subjects.