Question

Fill in the blank with a suitable verb:
I missed the bus this morning so I _______ walked to school
A. Have to
B. Must
C. had to
D. Ought

Answer 1

Hint: A Modal verb is a type of verb used to denote modality, i.e. possibility, ability, permission, request, ability, suggestions, order, duty, or advice. The base form of another verb that has semantic content is often followed by modal verbs.

Complete answer:
For describing an event, action, or condition, a verb is used. In a sentence, it is the grammatical core of the predicate.
An auxiliary verb is a verb used in the development of tenses, moods, tones, etc.
As skipped, option C is right, and walk indicates the use of had to.
As no other tense can be used here, the other alternatives are incorrect.
The correct answer to that question is C) Had to

Additional Information:
Modals are special verbs that behave irregularly in English (also called modal verbs, modal auxiliary verbs, modal auxiliaries). They vary from standard verbs such as "job, play, visit ..." They provide additional details about the main verb 's function that follows it. They have a wide range of communicative positions.
Here are some features that modal verbs have:
1. They never alter their shape. You would not be able to add "s", "ed", "ing" ...
2. They are often preceded without "to" by an infinitive (i.e. the bare infinitive.)
3. They are used to indicate modality that allows speakers to express certainty, choice, willingness, duty, need, capacity,

Hence the correct answer is option ‘C’

Note: To answer this type of question you need to develop the basic understanding about the common modal verbs. Here is a list of modal verbs:
Can, could, may, might, will, would, shall, should, must
The verbs or expressions dare, ought to, had better, and need not behave like modal auxiliaries to a large extent and may be added to the above list.