Internal conflicts among the options provided are:
1. Frank feels guilty about not telling  his parents what happened at the party.
4. Dr. MacDougal can't decide whether to  waive his fees for a patient who is  struggling financially.
External conflicts are:
2. Mr. Farris’s letters to the editor of the  local newspaper turned into a very nasty  exchange with another reader.
3. Mark argues with his team members who  are angry because he missed practice  so often.
An internal conflict is a struggle within a character and occurs in their own mind about what to he/she should think or do.
External conflict refers to a struggle that occurs between the protagonist and some external force. Therefore, the force is outside the body of the protagonist.
