Which one of the following shows isogamy with non-flagellated gametes?

The number of values of $x$ in the interval $[0, 5\pi]$ satisfying the equation $3\sin^2x - 7\sin x + 2 = 0$ is

Two workers $A$ and $B$ are engaged to do a piece of work. Working alone,$A$ takes $8 \text{ h}$ more to complete the work than if both worked together. On the other hand,working alone,$B$ would need $4 \frac{1}{2} \text{ h}$ more to complete the work than if both worked together. How much time would they take to complete the job working together (in $text{ h}$)?

If $\triangle ABC$ is right-angled at $A$,then $r_2+r_3$ is equal to

$1+\frac{1}{3 \cdot 2^2}+\frac{1}{5 \cdot 2^4}+\frac{1}{7 \cdot 2^6}+\ldots$ is equal to

Which is the smallest blood vessel in the body?