A. Dorothy laughed a lot because 1) she lived in Kansas. 2) her aunt and uncle were very serious. 3) she was a happy girl.

Решение:

В тексте сказано: "She was a happy girl and she had a funny dog Toto. She played with him every day after she helped her aunt about the house.". Из этого следует, что Дороти была счастливой девочкой.

Ответ: 3) she was a happy girl.