In America, the school day usually starts at 9a.m. and 1at about 4 p.m. The school subjects are different from 2. In China, we always have Chinese, maths, English, P.E. and so on. But in America, students have more lessons, such as 3 and driving lessons. Their school life isn't just about study. They have 4things to do than the Chinese students do. There 5 many clubs in American schools, too. If the students are6in sports, they can join different sports clubs. From 2:30 p.m.74 p.m., they do different things in different clubs.

    Maybe you think English is very popular in the world,8 American students don't need to learn any 9 language. But that's not true, American children from the age of seven 10 learn a foreign language. For example, they learn French or Chinese.

如图，在菱形ABCD中，AB=BD，点E、F分别在BC、CD上，且BE=CF，连接BF、DE交于点M，延长ED到H使DH=BM，连接AM，AH，则以下四个结论：

①△BDF≌△DCE；②∠BMD=120°；③△AMH是等边三角形；④S_{四边形ABMD}= $\frac{\sqrt{3}}{4}$ AM²．

其中正确结论的个数是（　　）