It is standard practice to try and answer an incoming telephone call:
a. after the first ring.
Ob. before the second ring.
Oc. before the third ring.
Od. before the fourth ring.
Oe. before the fifth ring.
a. after the first ring.
Ob. before the second ring.
Oc. before the third ring.
Od. before the fourth ring.
Oe. before the fifth ring.