In a contraction, the apostrophe should always be placed a. just before the last letter. b. immediately after the last letter. c. between the first word and the second word. d. where the missing letters would be.

The correct answer is D. where the missing letters would be

Explanation:

In the English language, a contraction is a shortened form of two words created by omitting certain letters of them and placing an apostrophe ('), which is a punctuation mark that shows letters in a word have been omitted. In the English language, contractions are common as these made language more concise and simple. However, contractions should be avoided in the case of formal speaking or writing. Examples of contractions include words such as "don't" which is created by combining the words "do" and "not" or "I've" created by combining "I" and "have". Considering the apostrophe is used to show one or more letters have been omitted in contractions, this punctuation mark should always be placed "where the missing letter would be", which means its location in contractions varies according to the letters that have been omitted.

because each is self-sufficient.  

the answer a: perseverance !