Complete the sentence by filling in the blank with the correct tenses from the given choices by indicating your option.
The Prime Minister _________to visit the hospital tomorrow.
The Prime Minister is to visit the hospital tomorrow.
In the given context "is to"/"are to" grammatical structure is often used to state officially mandated arrangements, plans, or regulations. In the present tense, they evoke the sense of a definite expectation that the action or activity referred to will be undertaken or will take place in the near future. Therefore 'is' is the most appropriate choice while other options don't fit.