O'level's to A's/A Level

[emkay]

hey everyone, how's it going? i guess not too bad! lol, okay so the thing which im confused about is that, i did'nt give chemistry in O'level's and nor was i going to take it in A's/A Level but now im at this stage where i have to take chemistry for A's/A Level, the point is that would i be asked for my previous O'level Result when i'll apply for Under-graduation? and how can NOT GIVING Chemistry in O'level's affect in A'S/A Level or after?
bless*