Why is getElementsById am illegal selector?

Question

One of the questions in a challenge i played on this platform was the above and i was just wondering how it is illegal?

Answer 1

You done a spelling mistake
It should be
getElementById
Not getElementsById
^
There is no s

Answer 2

getElementById and getElementsById aren't the same :3

Answer 3

Nope. Its elements i just checked again

Answer 4

Ahh im stupid thanks guys