The energy of the electron in the first orbit of $He^{+}$ is $-871.6 \times 10^{-20} \ J$. The energy of the electron in the first orbit of hydrogen would be

Which of the following $statement(s)$ is/are correct?
$(i)$ All living organisms have the ability to respond to environmental stimuli,which could be physical,chemical,or biological.
$(ii)$ Plants respond to external factors like light,water,temperature,other organisms,pollutants,etc.
$(iii)$ Photoperiod affects the process of reproduction.
$(iv)$ Human being is the only organism who has self-consciousness.

Which of the following is a single-membrane bound organelle?

The centre of mass of three particles of masses $1 ~kg, 2 ~kg$ and $3 ~kg$ is at $(2,2,2)$. The position of the fourth mass of $4 ~kg$ to be placed in the system so that the new centre of mass is at $(0,0,0)$ is:

The equation of the plane passing through $(1, 1, 1)$ and $(1, -1, -1)$ and perpendicular to $2x - y + z + 5 = 0$ is

The value of $\cos 15^{\circ} \cos 7.5^{\circ} \sin 7.5^{\circ}$ is