Which of the following reactions is correct?

$\Delta \lambda$ is the difference between the wavelength of the $K_{\alpha}$ line and the minimum wavelength of the continuous $X$-ray spectrum when the $X$-ray tube is operated at a voltage $V$. If the operating voltage is changed to $V/3$,then the above difference is $\Delta \lambda^{\prime}$. Then:

How many $H$ atoms are present in $0.046 \, g$ of ethanol $(C_2H_5OH)$?

If $A$ is a non-zero square matrix of order $n$ with $\operatorname{det}(I+A) \neq 0$ and $A^3=O$,where $I$ and $O$ are the unit and null matrices of order $n \times n$ respectively,then $(I+A)^{-1}$ is equal to

$A$ diode detector is used to detect an amplitude-modulated wave of $60\%$ modulation by using a capacitor of capacity $250 \text{ pF}$ in parallel with a load resistance of $100 \text{ k}\Omega$. Find the maximum modulation frequency which could be detected by it.