Having trouble with an IFR test question;
It reads,
What is the minimum increase in opacity of the surface based layer at
Fredericton (YFC), in order for it to constitude a ceiling?
METAR CYFC 132100Z 260010KT 2SM -RA BR BKN090 08/07 A2953 RMK
FG5SC1 SLP994

Choices:
a) none, it alreadi constitudes a ceiling
b) 2/8
c) 3/8
d) 1/8

The answer is c.
Anyone know why?