It’s 20 past 9 (Alternative clock system).

21:20

It’s 20 past 9.

Correct answer

20:40

It’s 20 to 9.

Error: mirror minute hand about the vertical axis

21:16

It’s 16 past 9.

Error: read minutes as hours with ‘past’ or ‘to’

16:45

It’s a quarter to 5.

Error: confuse hour and minute hands