An anther having four microsporocytes shall produce pollen grains

Answer: Option D

An anther having four microsporocytes shall produce 16 pollen grains.
In heterosporous seedless vascular plants, modified leaves called microsporophylls bear microsporangia containing many microsporocytes that undergo meiosis, each producing four microspores.
Therefore an anther with four microsporocytes will produce a total of 16 pollen grains.