$1$ Giving reasons by explaining $($very briefly$),$ why?

$($a$)$ The thyristors are not transported without keeping anode and cathode terminal shorted.

$($b$)$ Only fast recovery diodes are advocated for freewheeling applications.

$($c$)$ AC$-$DC voltage doublers are not advocated for high power applications.

$($d$)$ Only $12$n $+1$ harmonics can exist in current for $12$ pulse rectifier.

$($e$)3$ phase$-$controlled bridge rectifiers transact quasi square current for the mains.

$($f$)$ Filter requirements for inverter reduces for bridge inverters with Unipolar switching as compared to Bipolar switching.

$|($g$)$ Single Phase Quasi square $(120-$ central aligned$)$ wave inverters do not have triplens $(3$rd harmonics and their multiples$).$

$($k$)$ DC$-$DC Boost converters are usually not recommended for operation beyond a gain of $3.$

$($i$)$ The requirement of capacitor at output of DC$-$DC boost converter is higher than that of buck converter.

$($j$)$ The range of the operation of the antiparallel thyristors connected in tandem with pure inductor fed from sinusoidal ac source is between $90-180$ to realize a variable inductor.

$($k$)$ Voltage stress of the switch used in the boost converter is very high as compared to that of buck converter.