Scurvy is caused by the deficiency of:

Xerophthalmia in children and nyctalopia (night blindness) in adults is caused by the deficiency of which vitamin?

$A$ man is said to be starving when

Which group of three of the following five statements $(I-V)$ is correct regarding beriberi?
$I.$ $A$ crippling disease prevalent among the native population of sub-Sahara Africa.
$II.$ $A$ deficiency disease caused by lack of thiamine (vitamin-$B_{1}$).
$III.$ $A$ nutritional disorder in infants and young children when the diet is persistently deficient in essential protein.
$IV.$ Occurs in those countries where the staple diet is polished rice.
$V.$ The symptoms are pain from neuritis,paralysis,muscle wasting,progressive oedema,mental deterioration and finally heart failure.

The deficiency of vitamin $B_{1}$ causes

Which is the best source for vitamin $B_1$?