【单选题】下列铵盐中,受热分解时不放出 NH3 的是
【判断题】空间数据库系统和工程数据库系统属于专用数据库系统。( )
【单选题】April 21 was the national memorial day ____ were killed in Yushu Earthquake on April 14 2010.
A.
in honor of any one who
B.
in celebration of those who
D.
in charge of no matter who
【单选题】Memorial Day is originally a day on which Americans honor the soldiers who died in .
D.
the American Civil War
【判断题】Memorial Day is a federal h oliday.
【判断题】目前已知的新型冠状病毒的最有效的传播方式是血液传播。