足月儿生后第1小时内呼吸频率是()。
A.20~30次/分
B.40~50次/分
C.60~80次/分
D.90~100次/分
E.100~110次/分
参考答案:C
_____a written permission, he had to write another letter to the president of the university.
A.Not giving
B.Not having been given
C.Having not given
D.Having not been given
水稻的花序属于()。
A.复总状花序
B.头状花序
C.复穗状花序
D.伞形花序