Which one feature is common to leech,cockroach,and scorpion?

The number of sigma $(\sigma)$ and pi $(\pi)$ bonds present in benzene respectively are:

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

Name the plant whose leaves are economically important and earn foreign exchange.

If $\alpha, \beta$ and $\gamma$ are the lengths of the altitudes of a $\triangle ABC$ with area $\Delta$,then $\frac{\Delta^2}{R^2}\left(\frac{1}{\alpha^2}+\frac{1}{\beta^2}+\frac{1}{\gamma^2}\right)$ is equal to

The length of a pendulum is measured as $1.01 \ m$ and the time for $30$ oscillations is measured as $1 \ \text{minute} \ 3 \ s$. The error in length is $0.01 \ m$ and the error in time is $3 \ s$. The percentage error in the measurement of acceleration due to gravity is: