Ordinary resolution at 'other general meeting'

Hi,

To the question in the mock exam: When a public company wishes to pass an ordinary resolution at ‘other general meeting’ to appoint a director celebrating her 72nd birthday how many days notice should normally be given?

a)21
b)7
c)28
d)14

The correct answer is 21. Why is not 14 if ordinary resolutions only require 14 days notice? I thought 21 days notice was only for AGM.

Thanks,