The correct option is
C Theophrastus
The science which deals with the study of plants is known as botany. Theophrastus is known as the father of botany. He was a scientist and a Greek philosopher. He studied the plants and wrote many books on systematic and organization of tissues in plants. Due to his valuable contribution in the field of botany, he is regarded as the father of botany. So, the correct answer is 'Theophrastus'