A:1个
B:2个
C:3个
D:4个
证明:∵BE平分∠ABC,∴∠1=∠3. (____)
又∵∠1=∠2(已知),∴____ =____( 等量代换),
∴____∥____(____)
∴∠AED=∠C (____).
10+9=____
10+____=17
10+____=11
10+____=12