Which of the following hydroxides is acidic?

$A$ telescope has an objective lens of focal length $150 \ cm$ and an eyepiece of focal length $5 \ cm$. If a $50 \ m$ tall tower at a distance of $1 \ km$ is observed through this telescope in normal setting,the angle formed by the image of the tower is $\theta$,then $\theta$ is close to..... (in $^{\circ}$)

In which of the following reactions is benzaldehyde formed from benzoyl chloride and hydrogen in the presence of $Pd/BaSO_4$?

Two capacitors $C_1 = 2 \, \mu F$ and $C_2 = 4 \, \mu F$ are connected in a circuit as shown in the figure. The potential difference $(V_A - V_B)$ is.....$V$.

What will be the ratio of de-Broglie wavelengths of a proton and an $\alpha$-particle of the same energy?

Serum differs from blood in