If the system of equations $x + 2y - 3z = 1$,$(k + 3)z = 3$,and $(2k + 1)x + z = 0$ is inconsistent,then the value of $k$ is:

$A$ small quantity of solution containing $Na^{24}$ radionuclide 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 $1\, curie = 3.7 \times 10^{10}$ disintegrations per second and $e^{-\lambda t} = 0.7927$; where $\lambda$ is the disintegration constant).

In the Bohr series of lines of the hydrogen spectrum,the third line from the red end corresponds to which one of the following inter-orbit transitions in an atom of hydrogen?

If $|a|=1, |b|=2$ and the angle between $a$ and $b$ is $120^{\circ}$,then ${(a+3b) \times (3a-b)}^2$ is equal to

Which final cytochrome in the respiratory chain donates electrons to oxygen?

Crystalline sodium chloride is an insulator of electricity because $......$