Respuesta :
Answer:
A. most difficult
Explanation:
There are three degrees of comparison of adjective which are positive, comparative and the superlative degree. In a positive degree of comparison, no comparison is made. In Comparative degree, the comparison is made between two things or person. In superlative degree, more than two things are compared. In the given sentence, more than two things are compared, hence the superlative degree of comparison will be used. The superlative degree of 'difficult' will be 'most difficult'.