The product $\begin{array}{*{20}{c}} {CH_2 - O - COCH_3} \\ {|} \\ {CH_2 - O - COCH_3} \end{array}$ is obtained by the reaction of which of the following?

$A$ ball of density $\rho$ is released from deep inside a viscous liquid of density $2\rho$. It will move up:

Which of the following is a primary halide?

$\Delta \lambda$ 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:

Which of the following is not included in the five-kingdom classification system?

$A$ galvanometer may be converted into an ammeter or a voltmeter. In which of the following cases will the resistance of the device so obtained be the largest?