All these answers can be answered by looking at the "Circle of Fifths".
It's like a clock. For example, 1 o'clock = 1 sharp. 2 o'clock = 2 sharp.
Since G is at 1 o'clock, it will have 1 sharp.
The order of sharps is FCGDAEB.
So, if we are looking at G, it has one sharp, therefore the sharp...