Which of the following is not a polymer?

The parabola with directrix $x+2y-1=0$ and focus $(1,0)$ is

If $\cos x = \tan y$,$\cot y = \tan z$ and $\cot z = \tan x$,then $\sin x$ equals to

The filiform apparatus is a characteristic feature of which of the following?

An ovule which becomes curved so that the nucellus and embryo sac lie at a right angle to the funicle is called:

In the circuit shown in the figure,the reading of the voltmeter is $V_1$ when only $S_1$ is closed,the reading of the voltmeter is $V_2$ when only $S_2$ is closed,and the reading of the voltmeter is $V_3$ when both $S_1$ and $S_2$ are closed. Then: