What is the percentage of lead in a lead pencil (in $,\%$)?

$A$ proton (mass $m$ and charge $+e$) and an $\alpha$-particle (mass $4m$ and charge $+2e$) are projected with the same kinetic energy at right angles to a uniform magnetic field. Which one of the following statements is true?

In the given transistor circuit,the base current is $35\,\mu A$. The value of $R_b$ is.......$k\Omega $

In the compound $M-O-H$,the $M-O$ bond will be broken if

Which of the following pairs of species is used in the preparation of antacid medicines?

The contrapositive of the statement "If two numbers are not equal,then their squares are not equal" is