Answer:
A, C
Explanation:
If it is inversely proportional then y = k/x
Let's try one by one for the options. (im replacing y and x in the equation and finding k to see if k is the same all throughout) 
A. 
6 = k/1 (k=6)
3 = k/2 (k=6)
2 = k/3 (k=6)
1.5 = k/4 (k=6)
Yes! It's the same everywhere so this is correct! 
B. 
7.5 = k/2 (k=15)
5 = k/3 (k=15)
3 = k/5 (k=15)
2 = k/7 (k=14)
For the last one k is not the same so nope. It is wrong. 
C. 
24 = k/1 (k=24)
8 = k/3 (k=24)
k = 6×4 = 24
k = 24×1 = 24
This is correct too.
D. 
k = 0.1×200 = 20
k = 0.3×40 = 12
k = 0.8 × 25 = 20
We can already see that k is not the same everywhere. 
Only A and C, x and y are inversely proportional for all of the values