$MALT$ constitutes about what percentage of the lymphoid tissue in the human body (in $, \%$)?

Person '$A$' cannot step out of his house. He has to spend his entire life in sterile isolation; otherwise, he would quickly contract a fatal infection. This person has almost no effective immune system. This disease is also called '$baby$ $in$ $a$ $bubble$ $syndrome$'. Identify the disease this person '$A$' is suffering from.

Assertion: Interferons are a type of antibodies produced by body cells infected by bacteria.
Reason: Interferons stimulate inflammation at the site of injury.

The antibodies are formed in

Match the pairs:

Column $I$ (Type of Immunity)	Column $II$ (Example)
$i$. Natural acquired active	$a$. $BCG$ Vaccine
$ii$. Artificial acquired active	$b$. Immunity against measles
$iii$. Natural acquired passive	$c$. Colostrum
$iv$. Artificial acquired passive	$d$. Injections against rabies

Select the correct option from the following:

Which of the following is true regarding $T$-lymphocytes in mammals?