Which of the Following Is True About Second-Language Learning

Which of the following is true about second-language learning?

A) For adolescents and adults, new vocabulary is easier to learn than new sounds or new grammar.
B) Children's ability to pronounce words with a native-like accent in a second language typically increases with age.
C) Sensitive periods for learning a second language are constant across different language systems.
D) Adults tend to learn a second language slower than children, but their final level of second-language attainment is higher.