挑战习题
1/5单选题
难度:

1.

中,分别为的中点,,求的长为(  )


A

B

C

D

提示1:
PHA+6K6+IDxpbWcgc3JjPSJodHRwczovL3AxLnFpbmdndW8uY29tL0cxL00wMC8wMS9DQy9yQkFDRkZNTlRwR1MxQmEzQUFBQ1VWeWZUQ0EwNjUucG5nIiBkYXRhLWNrZS1zYXZlZC1zcmM9Imh0dHBzOi8vcDEucWluZ2d1by5jb20vRzEvTTAwLzAxL0NDL3JCQUNGRk1OVHBHUzFCYTNBQUFDVVZ5ZlRDQTA2NS5wbmciIGhlaWdodD0iMjEiIHdpZHRoPSIxMTgiPu+8jOeEtuWQjuWIqeeUqOWLvuiCoeWumueQhuihqOekukFEwrLvvIxCRcKy77yM5pW055CG5b6X5Ye6YcKyK2LCsueahOWAvO+8jOi/m+iAjOaxguWHukFCPC9wPg==
正确答案:QQ==
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