Which of the following statements about policy-based IPsec tunnels are true? (Choose two.)
A. They support GRE-over-IPsec.
B. They can be configured in both NAT/Route and transparent operation modes.
C. They require two firewall policies: one for each direction of traffic flow.
D. They support L2TP-over-IPsec.
https://fortinetweb.s3.amazonaws.com/docs.fortinet.com/v2/attachments/4afb0436-a998-11e9-81a4-00505692583a/FortiOS-6.0-Handbook.pdf
See this handbook page 1232
Correct options B & D
B, D is correct. See FortiGate Infrastructure Study Guide 6.0 Page 204
page 205 of infrastructure guide