油菜感染霜霉病后，花梗顶部肿大弯曲,呈____状。
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三大类型油菜中，芥菜型油菜较抗霜霉病，甘蓝型次之，白菜型最感霜霉病。
A. 对
B. 错
芥菜型油菜感染病毒后表现系统枯斑。
A. 对
B. 错
霜霉病病菌均以卵孢子越冬或越夏。
A. 对
B. 错
Choose the answer that best completes the statement or answers the question.Under the policy of segregation, the aboriginal people ___________.
A. wereforcibly removed from their own land
B. were allowed to have their own land as private reserves
C. were often employed by the Christian Church
D. were considered to be intellectually exploitable
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