Your answer is B, (t4 - rs5) (t8 + rs5t4 + r2s10)
let me know if you need an explanation :)
Here, triangle AEN and ALG are similar.
We know that the ratio of corresponding sides of two similar triangles are equal. So,

Answer: A. 1.2
Step-by-step explanation:
Given : Sample size : n= 64
Standard deviation: 
The formula to find the standard error of mean is given by :-

Therefore, the standard error of the mean= 1.2
Hence, A is the right option.