Cho tứ giác ABCD nội tiếp (O;R). AC vuông góc với BD và AC cắt BD tại I. Gọi trung điểm của AB là M. Chứng minh rằng MI vuông góc với DC

Cho ABC nội tiếp (O) và trực tâm H. Kẻ đường kính AD a) Chứng minh rằng BHCD là hình hành b) Gọi E là điểm đối xứng của H qua O. Chứng minh rằng vecto HA + HB + HC = Vecto HE

Trong tự nhiên, hidro có 2 đồng vị: H 1/1 và H 1/2; O có 3 đồng vị O 8/16; O 8/17; O 8/18. Hỏi có bao nhiêu loại phân tử nước ?

Every possible means ___ to prevent the air pollution, but the sky is still not clear.

_____ you discover his weakness, the easier the watch should become.  

______ all birds, penguins are the most fully adapted to water and extreme cold.

Emily: “Thanks for giving me a ride to work today”. Brian: “ _______ I was heading this direction anyway.”A. You don’t need to.    B. Yes, thanks. C. No worries.        D. I’d love to. 

The murdered man is thought to . . . . . . . . .. known the identity of his killer.

A be              B being                                                 C having                                                                             D have

50. Although he seemed convincing. I was somewhat suspicious. . .. his over-confident manner.

A of                                 B with                                C by                                                                                    D for

Cứu mình với :(

It was such a stale cake that the boy could not eat it.

 The cake was not...........................................................................................................................

Write a paragraph about precautions against covid-19 ( 140 words )