Answer:
Options a and c
Step-by-step explanation:
A unit circle is one which has origin as centre and radius as 1.
The equation of the unit circle would be

Thus we find that any point satisfying the above equation lies on the unit circle
Let us try the given points one by one
a)
. Hence lies on the circle
b) (1,1)
Cannot lie on circle since 
c)
. Hence lies on the circle
d) 
Hence does not lie on the circle
Only option A,C are right