D )3.Linda's biggest challenge is how to behave at the party. A.learning B.to learn C.to learning D.A and B B )4.You wouldn't believe how my English with his help. A.quick,improve B.quickly,has improved C.quickly,improve D.quick,has improved 导航页导航页 ( )3.Linda’s biggest challenge is_______how to behave at the party. A. learning B. to learn C. to learning D. A and B ( )4.You wouldn’t believe how_________ my English with his help. A. quick, improve B. quickly, has improved C. quickly, improve D. quick, has improved D B