Which of the following sentences does not use capitalization correctly?

A Dad said he would pick us up.

B Planet Earth is in trouble these days.

C I find this English course challenging.

D My Mom is a great cook

D) My Mom is s good cook is capitalized incorrectly. Words like "mom" or "grandpa" should be capitalized when they are used in place of the person's name (Grandma, will uou take me to the zoo?"), but not when paired with a posessive like my oe her (Suzie took her grandms to the zoo.)