What do $C$ and $Si$ possess among the following?

Two sources of sound placed close to each other are emitting progressive waves given by $y_1 = 4 \sin(600\pi t)$ and $y_2 = 5 \sin(608\pi t)$. An observer located near these two sources of sound will hear:

The formula of the product formed when sodium thiosulphate solution is added to silver bromide is:

Assertion $A$: An astronaut inside a massive spaceship orbiting around the Earth will experience a finite but small gravitational force.
Reason $R$: The centripetal force necessary to keep the spaceship in orbit around the Earth is provided by the gravitational force between the Earth and the spaceship.

Which complex is most stable?
Where $k_d = \text{Dissociation constant}$

$A$ small quantity of solution containing $Na^{24}$ radio nuclide of activity $1 \, \mu Ci$ is injected into the blood of a person. $A$ sample of the blood of volume $1 \, cm^3$ taken after $5 \, hours$ shows an activity of $296$ disintegrations per minute. What will be the total volume of the blood in the body of the person? Assume that the radioactive solution mixes uniformly in the blood of the person. (Take $1 \, Ci = 3.7 \times 10^{10} \, dps$ and $e^{-\lambda t} = 0.7927$; where $\lambda$ = disintegration constant)