Final answer:
In the given sentence, 'pleased' means Lonnie made his sister happy by giving her a compliment, thus the correct option is b) Complimented.
Step-by-step explanation:
In the sentence 'Lonnie pleased his little sister by saying, 'You're so smart!',' the word pleased means that Lonnie did something that made his little sister happy or satisfied. Among the given options, the best fit for the meaning of pleased in this context is option b) Complimented. This is because saying 'You're so smart!' is a way of giving someone a compliment, which typically pleases the person receiving it. Therefore, Lonnie complimented his little sister, resulting in her feeling pleased.