Choose one of the following options:
Answer call, go to 1a.
Reject call, go to 1b.
Silence the incoming call alert, go to 1c.

Tap and drag the accept call icon right.

Tap and drag the reject call icon left.

Tap the upper or lower part of the Volume key when you get a call.
The incoming call alert is silenced without the caller hearing it, but the call continues until it's ended or diverted.