Image A, B and C is having a conversation. There can be 4 scenes:
A: Don't put too many balls in the box. B: How many is/are too many?
A: Don't put too many balls in the box. B: How many balls is/are too many?
C: How many is/are not important. Have it your own way.
C: How many balls is/are not important. Have it your own way.
Should I use "is" or "are" in these "how many..." sentences?