Which is true concerning a required watch on VHF Ch-16?

When a vessel is in an A1 sea area and subject to the Bridge-to-Bridge act and in a VTS system, a watch is required on Ch-16 in addition to both Ch-13 and the VTS channel.

It is not compulsory at all times while at sea until further notice, unless the vessel is in a VTS system.

When a vessel is in an A1 sea area and subject to the Bridge-to-Bridge act and in a VTS system, a watch is not required on Ch-16 provided the vessel monitors both Ch-13 and the VTS channel.

It is not always compulsory in sea areas A2, A3 and A4.

Which is true concerning a required watch on...