Trong bản vẽ kĩ thuật, nét đứt dùng để vẽ: *

3 điểm

a,đường tâm, đường trục đối xứng.

b,đường bao khuất, cạnh khuất.

c,đường dóng, đường trục đối xứng.

d,đường kích thước, đường dóng.

mn giúp mik vs mik đg cần gấp

cân bằng PTHH sau : 

a, Na+O2 => Na2O

b, P2O5+H2O => H3PO4

c, HgO => Hg+O2 

d, Fe(OH)3 => Fe2O3 + H2O

mn giúp mik vs ạ

X. Finish each of the following sentences in such a way that it means exactly the same as
the sentence printed before it.
1. They recruited very few young engineers.
Hardly ___________________________________________________________________
2. Only two out of the five rooms we have booked have air conditioning.
We have booked five rooms, only ______________________________________________
3. Jane seems to come to the performance late.
It looks ___________________________________________________________________
4. I could hold a big party due to Mom’s help.
Had it ____________________________________________________________________
5. Success depends on hard work.
The harder ________________________________________________________________
6. Fiona was so disappointed that she could not keep on working.
Such _____________________________________________________________________
7. Although Richard is competent in his work, he does not know how to deal with this client.
Competent ________________________________________________________________
8. It was wrong of you to allow a four-year-old child to walk home alone.
You should ________________________________________________________________
9. I could realize how important the family is only after I left home.
Not until __________________________________________________________________
10. Mrs. Green is proud of her son’s contribution to the play.
Mrs. Green is proud of what __________________________________________________