东北地区要发展的两种人工速生丰产林是 …()
A.红松、杨树
B.红松、紫椴
C.落叶松、红松
D.落叶松、杨树
D
东北林业的发展应坚持以营林为主,发展以落叶松和杨树为主的速生丰产林。
— _____________ do you get to school very early?
— Sometimes.[ ]
A. How often
B. How many
C. How far
D. How long
如何预防糖尿病病人发生低血压?