Which of the following will give 60 ml of 0.4 M NaOH solution?

The correct options are
A 20 ml 1.2 M NaOH solution is mixed in 40 ml water
B 20 ml of 1 M NaOH solution is mixed with 40 ml of 0.1 M NaOH solution
C 0.4 g of NaOH and 20 ml of 0.7 M solution of NaOH are added to 40 ml water
D 0.48 g of NaOH is added to 60 ml of 0.2 M NaOH solution
60 ml 0.4 M NaOH solution = 24 mmol
(a) 20 ml 1.2 M NaOH =24 mmol and vol = 20+40=60 ml
(b) 20 ml 1M+40 ml 0.1 M = 20+4 = 24 mmol
(c) 0.4 g=0.4/40=0.01 mol=10 mmol and 20 ml 0.7 M = 14 mmol, So total mmol = 24 mmol
(d) 0.48 g NaOH = 12 mmol of NaOH and 60 ml 0.2 M NaOH = 12 mmol; So total mmol = 24 mmol