The correct option is D I, II and III together
From III, we have : Rajan's basic salary = Rs 1550
From I, we have : Vasu's basic salary = Rs (1550+100) = Rs 1650.
From II. we have : Rajan's other allowances = RS 2000
and Vasu's other allowances = Rs 2050.
Vasu's monthly salary is ( 1650+2050 ) = Rs 3700
Thus, all the three statements are required.
option D