Maize/Wheat/Rice grain is

The correct option is A Fruit

The fruit in grass family Poaceae to which maize wheat and rice belong produce an indehiscent , simple dry fruit known as caryopsis. The grain found in the market is the fruit which encloses the seed and the embryo. A dried bud of maize/wheat/rice are not commercially valuable.

So, the correct answer is 'Fruit'.