Which of the following is the only taxonomic category that has a real existence?

In which of the following processes,the bond order has increased and paramagnetic character has changed to diamagnetic?

In the circuit shown in the figure,$K_1$ is open. The charge on capacitor $C$ in steady state is $q_1$. Now,the key is closed and at steady state,the charge on $C$ is $q_2$. The ratio of charges $q_1/q_2$ is

The $AT/GC$ ratio in human beings is (where $A=$ adenine,$T=$ thymine,$G=$ guanine,$C=$ cytosine).

If the roots of the given equation $(\cos p - 1){x^2} + (\cos p)x + \sin p = 0$ are real,then

$\lim _{x \rightarrow 0} \frac{4^x-9^x}{x(4^x+9^x)}$ is equal to