Which of the following minerals is not remobilized in plants?

Two different radioactive elements with half-lives $T_{1}$ and $T_{2}$ have undecayed atoms $N_{1}$ and $N_{2}$ respectively,present at a given instant. The ratio of their activities at this instant is

The statement $\sim (p \leftrightarrow \sim q)$ is

If $1, \log_9(3^{1-x} + 2), \log_3(4 \cdot 3^x - 1)$ are in $A.P.$,then $x$ equals

The equation of the sphere passing through the points $(1,0,0)$,$(0,1,0)$,and $(1,1,1)$ and having the smallest radius is:

At a certain place,the angle of dip is $60^{\circ}$ and the horizontal component of the earth's magnetic field $(B_H)$ is $0.8 \times 10^{-4} ~T$. The earth's overall magnetic field is