Refer to figure.
Figure A shows an array antenna. A series of vertically mounted antennas are connected to cover the full 360°. This gives the advantage of strengthening the sensitivity and signal, reducing interference, improving the coverage area and allowing directional sensing. In aviation they are used for VHF comms and VHF Direction Finding (VDF).

Figure B is hard to clarify, it may be a GPS receiver antenna or it may be an ADF antenna. If it was situated on the top of an aircraft it would most likely be a GPS antenna, and if on the underneath of an aircraft it would most likely be an ADF antenna.

Figure C shows an NDB mast antenna, with shorter antennas arranged horizontally on the top of a mast to give 360° coverage for the omnidirectional NDB signal. NDB antennas can also be a "T" type, which is simply an antenna suspended between two supporting masts, resembling a telephone wire. A "T" type is more powerful but requires a lot of space, whereas a mast type takes up less space but may lose some signal strength or accuracy.

Figure D shows a parabolic primary radar antenna, and an SSR array antenna is mounted on the top. This is a common sight at larger airports where the entire structure will rotate 360° to allow the bearing information required by primary radar to be measured. Parabolic antennas are also used in older Airborne Weather Radars (AWR), but AWR uses a much smaller antenna which does not have the SSR antenna on the top and it is not free to rotate 360° (so it doesn't cook the pilots).