Cho Δ ABC nhọn có hai đường cao AD và BE cắt nhau tại H ( D ∈ BC , E ∈ AC ) . a) Chứng minh : Δ CAD ᔕ Δ CBE . b) Chứng minh : HA . HD = HB . HE c) Chứng minh : góc BAD = góc DEB .

Supply the correct form of the word in parentheses to complete each sentence

1. A number of clean products contain _______________ chemicals.                                  (HARM) 

2. Da Lat is famous for the _______ beauty of its mountains and forests.                            (SCENERY)

3. Debris___________cleared by rescue teams.                                                                     (FINAL)

4. Do you know what _______ cause air pollution?                                                               (POLLUTE)