Introduction:

The given sentence states that "The mobile phone is the gift of science." In this sentence, the definite article 'the' is used before the words 'mobile phone' and 'gift of science.' This indicates that both 'mobile phone' and 'gift of science' are specific and known to the speaker and the listener.

Explanation:

To understand why option 'C' is the correct answer, let's analyze each option:

a) An, a: This option uses the indefinite article 'an' before 'mobile phone' and the indefinite article 'a' before 'gift of science.' However, in the given sentence, the speaker is referring to a specific mobile phone and a specific gift of science, so the indefinite articles are not appropriate here.

b) An, the: This option uses the indefinite article 'an' before 'mobile phone' and the definite article 'the' before 'gift of science.' Again, the use of the indefinite article is incorrect because the speaker is referring to a specific mobile phone. However, the use of the definite article before 'gift of science' is correct as it indicates a specific gift of science.

c) The, a: This option uses the definite article 'the' before both 'mobile phone' and 'gift of science.' This is the correct answer because 'the' is used to refer to specific and known objects or concepts. In this sentence, the speaker is referring to a specific mobile phone and a specific gift of science.

d) The, the: This option uses the definite article 'the' before both 'mobile phone' and 'gift of science.' While the use of the definite article is correct, it is redundant to use 'the' before both words. The sentence can be understood without repeating the definite article.

Conclusion:

The correct answer is option 'C' because it uses the definite article 'the' before 'mobile phone' and the indefinite article 'a' before 'gift of science.' This accurately conveys that the mobile phone being referred to is specific and known, while the gift of science is a general concept.