點分C or G or F ...大調

I assumed you are talking about key signatures..

C major (大調): the key signature is nothing
and the chord would be C E G
G 大調: with 1 #(sharp) on the high F
and the chord would be G B D
F 大調: with 1 b(flat) on the B
and the chord would be F A C


Notes:
for # key signature: to find out the key it present, you only need to look at the right-most # and add (1), then it your major key...
for example,
if the right-most # is on C, its D major
if the right-most # is on G, its A major..etc

for b(flat) key signature, look at the second right-most 'b', and that would be the major key.
for example:
if the second right-most b is on B, its B b(flat) major
if the second right-most b is on A, its A flat major..etc
the only exception is F major, which it only have 1 b on its key signature, the Bb, and that's also the fourth note of the chord.
--> the right-most b on the key signature also represents the fourth note of that major key.

hope this help...