题目

Luckily ______ to be no one under the tree when it broke down. A．it happened          B．there happened          C．there used          D．it had 答案：B电子琴能模仿各种乐器发出的声音，在技术上要解决的关键是能模仿各种乐器发出声音的（ ）A．音调B．音色C．响度D．音色和音调