What did the TAC engineer configure incorrectly?

Refer to the exhibit.

A new TAC engineer came to you for advice. A GRE over IPsec tunnel was configured, but the
tunnel is not coming up.
What did the TAC engineer configure incorrectly?

A.
The crypto isakmp configuration is not correct.

B.
The crypto map configuration is not correct.

C.
The interface tunnel configuration is not correct.

D.
The network configuration is not correct; network 172.16.1.0 is missing.