on board/ on the board of

[CarloSsS]

I just did a test (composed by a non-native speaker) and in the test, there was the following multiple-choice question:

There were a lot of people _________ the plane.

1. aboard of
2. on board of
3. on board
4. on the board of

I chose the answer 4. but according to the test, 3. is the only possible answer. What do the natives speakers of English think? Is really the 4th answer a wrong one?

[bhaisahab]

I just did a test (composed by a non-native speaker) and in the test, there was the following multiple-choice question:

There were a lot of people _________ the plane.

1. aboard of
2. on board of
3. on board
4. on the board of

I chose the answer 4. but according to the test, 3. is the only possible answer. What do the natives speakers of English think? Is really the 4th answer a wrong one?

Only #3 is correct.