True fruit is the fruit that is formed from the fertilized ovary of the flower and ovules get transformed into seeds.
False fruit is a fruit formed from other parts of the plant as well as the ovary, especially the receptacle, such as the strawberry or fig.
Mango develops from a ripened ovary and thus is called a true fruit. It is a kind of drupe.
Apple develops from a ripened thalamus and is a false fruit.
Strawberry develops from an aggregate of achenes and the edible part is thalamus. It is thus a false fruit.
The cashew nut eaten is actually the seed and the fruit that bears this seed is a false fruit.
So, the correct answer is 'Mango'.