Haploid plants are obtained from which of the following?

The disease known as fluorosis is caused by the reaction of fluorine with which of the following?

The area (in square units) of the region bounded by $x^2=8y$,$x=4$ and the $X$-axis is:

In which of the following pairs of categories is it more difficult to determine the relationship to other taxa at the same level, thus making the problem of classification more complex?

$A$ uniform rope of mass $0.1 ~kg$ and length $2.45 ~m$ hangs from a rigid support. The time taken by the transverse wave formed in the rope to travel through the full length of the rope is (Assume $g=9.8 ~m/s^2$) (in $~s$)

Which of the following is not a sex hormone?