Which hormone is produced by the placenta?

From which plant are flax fibers obtained?

Which of the following compounds will exhibit geometrical isomerism?

Which of the following pairs represents linkage isomerism?

If $f: R \rightarrow R$ is defined by $f(x) = \begin{cases} \frac{2 \sin x - \sin 2x}{2x \cos x}, & \text{if } x \neq 0 \\ a, & \text{if } x = 0 \end{cases}$,then the value of $a$ so that $f$ is continuous at $x = 0$ is

$A$ Carnot engine,having an efficiency of $\eta = 1/10$ as a heat engine,is used as a refrigerator. If the work done on the system is $10 \ J$,the amount of energy absorbed from the reservoir at a lower temperature is .......... $J$.