Which of the following oxides does not form an acidic aqueous solution?

If the decimal $0.d25d25d25\ldots$ is expressible in the form $n/27$,then $d+n$ must be

$A$ current-carrying solenoid is approaching a conducting loop as shown in the figure. The direction of the induced current as observed by an observer on the other side of the loop will be

Nitrobenzene on reduction using zinc in alkaline medium results in $X$. The number of $\sigma$ and $\pi$ bonds in $X$ is

The second and third rows of transition elements resemble each other much more than they resemble the first row. Explain why?

$A$ transistor having a $\beta$ equal to $80$ has a change in base current of $250 \mu A$. The change in collector current is: