Difference between considerably and relatively

[Spring]

Test No. incompl/advan-61 "Trains", question 8

On the day we travelled most people had decided to stay at home as the train was ......... empty.

(a) considerably
(b) related
(c) reliable
(d) relatively

Test No. incompl/advan-61 "Trains", answer 8

On the day we travelled most people had decided to stay at home as the train was relatively empty.

Correct answer: (d) relatively

Your answer was: incorrect
On the day we travelled most people had decided to stay at home as the train was considerably empty.
_________________________

Both relatively and considerably seem to be appropriate to use in the sentence above. Could you explain the difference of the two?

[Torsten]

The modifier considerably describes a great extent or degree so it wouldn't work in connection with the adjective empty.

TOEIC listening, photographs: A burglar

[MariaEbb]

Both the word consider and considerably puzzles me.
/Maria

[Dennisnguyen]

Hi,
I'm a little bit confused of the sense of "as" in the context.
is it the same meaning as "though"?
Please explain it to me.
dennis