确定造林密度的因素有哪些？
参考答案：
主要有经营目的、树种特性、立地条件、造林技术、经济条件等。
根据句意及汉语或首字母提示完成单词。
1. My mother invited a t _____ to teach me how to play the piano.
2. Don't be n _____ The exam is very easy.
3. We should always remember, "Practice makes p _____.
4. Look! There are _____ (几个的) boys playing basketball on the playground.
5. I have _____ (发现) that the most important requirement is to work hard if you want to get a good
grade.
发球时下列哪种情况不属于失误（）
A.站在底线上面发球
B.发球时助跑起跳发球
C.发球时觉得抛起的球不好打，接住后重新再抛起击球
D.发球时抛起的球挥拍未击到，球落地后重新再抛起击球
