Single quotation marks are used when you insert a quotation within a quotation. An example has been provided below:
The student said, 'I heard the teacher tell the class, "Don't forget to study for next week's exam," and then I heard the bell ring.'
If both single and double quotations appear at the end of the sentence, the period falls within both sets of quotation marks-as demonstrated in the following example:
The student said, "I heard the teacher tell the class, 'Don't forget to study for next week's exam.' "
