Where, if at all, should a comma be added in the following sentence?

many people believe that global warming is real but they are not sure what can be done about it.

after the word but
after the word real
no comma should be added.
after the word believe

2. where, if at all, should a comma be added in the following sentence?

maya is determined to go to medical school or join the peace corps after college.

after the word or
no comma should be added.
after the word corps
after the word school

3. where, if at all, should a comma be added in the following sentence?

when novelists set out to write a work of historical fiction they craft a story that takes place during a particular era in the past.

after fiction
after era
no comma should be added.
after story

4. where, if at all, should one or more commas be added in the following sentence?

many wealthy businesspeople for example may have no time to enjoy their money.

after example
after businesspeople and after example
no comma should be added.
after businesspeople

5. where, if at all, should a comma be added in the following sentence?

dogs that do not shed are often called hypoallergenic.

no comma should be added.
after dogs
after dogs and after shed
after shed

6. where, if at all, should one or more commas be added in the following sentence?

the country of haiti which gained its independence from france in the early 1800s has seen much political and economic hardship.

after haiti and after 1800s
no comma should be added.
after 1800s
after haiti

7. which change corrects the following sentence?

rachel claims to be a vegetarian, however, she eats seafood.

replace the comma after however with a semicolon.
delete the comma after however.
replace the comma after vegetarian with a semicolon.
delete the comma after vegetarian.

8. which change, if any, corrects the following sentence?

when the ball drops at midnight in new york city's times square, millions of americans on the east coast will celebrate the new year.

add a comma after coast.
delete the comma after times square.
change the comma after times square to a semicolon.
no change is necessary.

9. which change, if any, corrects the following sentence?

i made an appointment with an optometrist because, i need a stronger prescription for my glasses.

add a comma after optometrist.
no change is necessary.
delete the comma after because.
add a comma after optometrist and delete the comma after because.

10. which change, if any, corrects the following sentence?

psy, a korean entertainer had a worldwide hit in 2012 with the song gangnam style.

delete the comma after psy and add a comma after entertainer.
no change is necessary.
delete the comma after psy.
add a comma after entertainer.