The activity of a radioactive substance can be represented by various units. Select the correct option.

The graph between the instantaneous concentration $(N)$ of a radioactive element and time $(t)$ is:

The half-life of ${}_{92}^{238}U$ against $\alpha$-decay is $13.86 \times 10^{16} \,s$. The activity of a $1 \,g$ sample of ${}_{92}^{238}U$ is:

If the mass of a radioactive sample is doubled,the activity of the sample and the disintegration constant of the sample are respectively

$A$ radioactive sample has a half-life of $5$ years. The percentage of the fraction decayed in $10$ years will be (in $\%$)

The half-life of a radioactive nucleus is $50$ days. The time interval $(t_2 - t_1)$ between the time $t_2$ when $\frac{2}{3}$ of it had decayed and the time $t_1$ when $\frac{1}{3}$ of it had decayed is (in days):