Which of the following has the highest solubility product?

Which of the following statements is true?

$A$ man running round a race-course notes that the sum of the distances of two flag-posts from him is always $10 \ m$ and the distance between the flag-posts is $8 \ m$. The area of the path he encloses in square metres is (in $\pi$)

Phytochrome is a

The number of sigma $(\sigma)$ and pi $(\pi)$ bonds present in benzene respectively are:

Which one of the following is a stimulant?