Question

_____ god bless you .
A. Must
B. Can
C. May
D. Would

Answer 1

Hint:Modal Verbs inform us the speaker's attitude about what is being said or done. The word "modal" suggests that expressing emotion and mood is a way of expressing the speaker's attitude.
It's used in greeting cards and as a personal wish.

Complete answer:
The given sentence is an exclamatory sentence and generally the modal verb "may" is used in the case of wishing someone or hoping something for someone.
May has many uses in English: to seek permission ('may I go now?'); to suggest an opportunity ('I may see her tomorrow'); and another of its uses is to make it clear that a desire is being conveyed rather than a statement created. So while "God bless you" is very good English, "may God bless you" makes it clearer that a wish is being conveyed.
Lets see options :-
Must :- 'must' is used with a previous participle verb, this indicates a past possibility or while saying something necessity thus this option is wrong.
Can :- The word "can" is used to indicate that something will and will be done or permitted to be done thus this option is wrong.
May :- uses is to make it clear that a desire is being conveyed rather than a statement created. So while "God bless you" is very good English, "may God bless you" makes it clearer that a wish is being conveyed thus this option is right.
Would :- When we report a past conversation, we always use 'would'-that is, we say what someone said in the past. Thus this option is wrong too.

Hence the correct answer is option C.

Note:God bless you (variants include God bless you or bless you is a common English phrase widely used in various contexts to wish an individual blessings,particularly as an answer to a sneeze, and also when parting or writing a valediction.
The phrase has been used by Jews in the Hebrew Bible (cf. Numbers 6:24) and by Christians as a blessing, a blessing, since the early Church.