Answer: B. 6 cm
Step-by-step explanation:
First we take down the information given to us,
distance from the lens to the image (v) = 24cm
distance from the original object to the lens (u) = 8cm
So using the formula
1/u + 1/v = 1/f
Where f is the focal length
So we just input our information
1/8 + 1/24 = 1/f
Therefore;
3/24 + 1/24 = 1/f
4/24 = 1/f
1/6 = 1/f
f = 6
Our focal length = 6cm