Answer:
In the sentence:
The truth is that whenever I eat an orange or a pear, I get very thirsty.
C. The
Is the definite article
Step-by-step explanation:
The definite article is always going to be the word "the" its characteristic is to provide a grade of classification to the following noun. On the other hand, there are two indefinite articles the first one is "A" and the second one is "an" they also classify something but the difference is that the definite article declares that the object we are talking about is the only one. For example.
He is the pirate. (here we use an absolute, specifying that there are no more like him)
He is a pirate. (here there is no absolute, there could be more like him)