Which of the following sentences is correctly punctuated?
A. A working student's best friend is her phone.
B. Several car's bumpers were crushed after the collision.
C. Tom's and Anne house is beautiful.
D. The ponys' saddle is so pretty.
Option A is correctly punctuated. It uses the possessive form "student's" to indicate that the friend belongs to the working student.
The possessive apostrophe is placed after "student" and before the "s" to indicate that the friend is singular and not plural.
Therefore, the Correct Answer is A.