在“学生-选课-课程”数据库中的3个关系如下：S（SNO, SNAME, SEX, AGE）； C（CNO, CNAME, TEACHER）；SC（SNO, CNO, GRADE），查询年龄大于19岁的女学生的学号。若用关系代数表达式来表示为（ ）。 A: ПSNO (σSEX=’女'(S) -σAGE<=19(S) ) B: ПSNO (σSEX=’女'(S) ∩ σAGE>19(S) ) C: ПSNO (σSEX='女'∧ AGE>19(S)) D: ПSNO (σSEX=’女’(S) ∪ σAGE>19(S) )

GPS时与协调世界时相差() A: 10s B: 15s C: 19s D: 逐年增大

​GPS时与协调世界时相差()‌ A: 10s B: 15s C: 19s D: 逐年增大

某患者APTT为52s/35s，PT为19s／11s，提示可能是以下哪组凝血因子缺陷

What's the time in Beijing when it's 10:00 a.m. in Sweden in Winter? A: 16:00 B: 17:00 C: 18:00 D: 19:00

完形填空 11 morning, everyone. 12 Grace. Look(看)!This is a 13 . It's a nice pen. What 14 is it? 15 yellow and white. And 16 this in English?It's 17 . It's 18 jacket. That's a ruler. 19 ruler is 20 .16．A．how B．what's C．what A: how B: what's C: what

Passage TwoQuestions 19 to 21 are based on the passage you have just beard. A: Preparing children academically. B: Developing children’s artistic interest. C: Tapping children’s potential. D: Shaping children’s character.

The country’s biggest e-commerce giant Alibaba says gross merchandise volume reached (  ) at 3:19 pm Beijing time.

完形填空 11 morning, everyone. 12 Grace. Look(看)!This is a 13 . It's a nice pen. What 14 is it? 15 yellow and white. And 16 this in English?It's 17 . It's 18 jacket. That's a ruler. 19 ruler is 20 .19．A．An B．The C．A A: An B: The C: A

19已知R=10Ω,C=2F的一阶电路,其时间常数=____s;已知一阶RL电路的R=10Ω,L=2H,则其时间常数=____s。