The correct option is C 750 ml
Given: 1 l=1000 ml
34 ml is nothing but one half litre and one quarter litre.
Quarter is half of half.
Half of 1000 ml is 500 ml, half of 500 ml is 250 ml.
The half of half which is quarter of 1000 ml is 250 ml.
Now, 34 l= Half litre + Quarter litre
=500 ml+250 ml=750 ml