A. Attitudes can't be learned from other people.
B. Negative attitudes can't be changed.
C. There's one fundamental way of acquiring attitudes.
D. Positive attitudes can help us learn more quickly.
D, when you're happier and in a better mood, you can learn better. When you're in a bad mood you basically don't want to do much, but when you are in a good mood, or have a positive attitude, you can do your best.