Hint- A statement is a meaningful declarative sentence that is either true or false.
Now as going by the definition of a statement, it should have a meaning which is either true or false .The important point is that all statements claim something or make a point , for example if you witness a crime then you make a statement to a police which is obviously meaningful.
So coming to the question part
$(1)$May God bless you
Is not a statement as it is not certain, it’s written may god bless you which means there is no certainty that god will bless that person . Hence it needs to be either true or false, but however it is not.
$(2)$Rose is a flower
It is a statement as Rose is certainly a flower and it is universally true, there is no uncertainty for this claim. Thus it satisfies the definition of a statement.
$(3)$Milk is white
It is also a statement as ‘milk is white’ is absolutely true, there is no doubt regarding the legitimacy of this line thus it also satisfies the definition of a statement.
$(4)$1 is a prime number
It is also a statement as 1 is a prime number, it is divisible by itself only hence this line is absolutely true and thus satisfies the definition of a statement.
Note-In these types of questions the basic definition of a statement helps distinguish various options given. One needs to have the basic understanding of the definition of statement to figure out the right answer amongst various options given.