Explanations:Demonstrative determiners are a type of determiner used in English to indicate the proximity of a noun to the speaker or listener. There are four demonstrative determiners in English: "this," "that," "these," and "those." Each of these words is used to specify the distance of the noun from the speaker or listener, and they are used with different types of nouns.
"This" is used for singular, countable nouns that are near the speaker. For example, if you are pointing to a shirt that is close to you, you would say, "This shirt is blue." The word "this" indicates that the shirt is close to the speaker, and it is singular and countable.
"That" is used for singular, countable nouns that are farther away from the speaker. For example, if you are pointing to a shirt that is across the room, you would say, "That shirt is blue." The word "that" indicates that the shirt is farther away from the speaker, and it is singular and countable.
"These" is used for plural, countable nouns that are near the speaker. For example, if you are pointing to multiple shirts that are close to you, you would say, "These shirts are blue." The word "these" indicates that the shirts are close to the speaker, and they are plural and countable.
"Those" is used for plural, countable nouns that are farther away from the speaker. For example, if you are pointing to multiple shirts that are across the room, you would say, "Those shirts are blue." The word "those" indicates that the shirts are farther away from the speaker, and they are plural and countable.
In the given sentence, "He wants _____ blue shirt," the noun "shirt" is singular and countable, and it is implied to be near the speaker. Therefore, the correct demonstrative determiner to use is "this." The sentence "He wants this blue shirt" correctly indicates that the shirt is close to the speaker and is singular and countable.
It is important to note that the other options provided, "ce," "ces," and "cet," are not English words. They are demonstratives in French, and they do not apply to the English sentence structure. "Ce" is used before masculine singular nouns in French, "ces" is used before plural nouns in French, and "cet" is used before masculine singular nouns that begin with a vowel sound in French. None of these French demonstratives are applicable in the context of the English sentence.