Which of the following is a herbicide?

Which of the following compounds will absorb the maximum quantity of heat when dissolved completely in the same amount of water? The heats of solution of these compounds at $25 \ ^\circ C$ in $kJ/mole$ of each solute is given in brackets.

What is the function of the algal component in a lichen?

The first step of taxonomy is .......... .

$A$ ball is dropped from a height of $20 \ m$ above the surface of water in a lake. The refractive index of water is $4/3$. $A$ fish inside the lake, in the line of fall of the ball, is looking at the ball. At an instant, when the ball is $12.8 \ m$ above the water surface, the fish sees the speed of the ball as ........ $m/s$ $[g = 10 \ m/s^2.]$

Which of the following is not a polymer?