如图所示，物块M在光滑斜面上从A匀速滑到C，速度v=2m/s，其中AB=6m，AC=10m，物块M重GM=100N，物块m重Gm=40N （不计滑轮重，绳重，绳与滑轮间摩擦）求：
平行四边形ABCD的对角线相交于点O，分别添加下列条件：①∠ABC=90°；②AC⊥BD；③AB=BC；④AC平分∠BAD；⑤AO=DO．使得四边形ABCD是矩形的条件有____。
—I'd like to, but I have a meeting to ______.
目前，我国居民储蓄余额突破43万亿元，成为全球储蓄总额和人均储蓄都最多的国家。与此存在因果联系的是（ ）
①家庭投资理财渠道较少
②存款储蓄的收益率在所有投资方式中最高
③我国的社会保障体系已非常完善与健全
④居民收入上升
A. She is in the kitchen.
B. She is cooking dinner.
C. Can she come with me?
D. Is that May?
Sally: Hello, This is Sally. ____
Paul: No. This is Paul.
Sally: Where is May?
Paul: ____
Sally: What is she doing?
Sally: We usually have dancing lessons in the evening. ____
Paul: I'm sorry. She can't have dancing lessons with you this evening. Sally: OK.
对细菌耐药性产生机理的叙述，不正确的是
