Answer: Option A
In computer programming, the term "case" refers to the capitalization of letters in a word or sentence. There are several different case styles used in computer programming, including:

• Sentence case: This style capitalizes only the first letter of the first word in a sentence, and leaves the rest of the words in lowercase. For example, "This is an example sentence."
• Title case: This style capitalizes the first letter of each word in a sentence, except for certain smaller words, such as "the," "and," and "of." For example, "This Is an Example Sentence."
• Upper case: This style capitalizes all the letters in a word or sentence. For example, "THIS IS AN EXAMPLE SENTENCE."
• Lower case: This style leaves all the letters in a word or sentence in lowercase. For example, "this is an example sentence."
• Toggle case: This style alternates the capitalization of letters in a word or sentence. For example, "ThIs Is aN ExAmPlE SeNtEnCe."

Based on the above definitions, it is clear that the option that converts only the first character of the first word of a selected sentence to capital is sentence case. This is because sentence case capitalizes only the first letter of the first word in a sentence, and leaves the rest of the words in lowercase.
Hence, the correct answer to the given question is option A, sentence.