题目

— How long _____ at this job ? — Since 2008.    A. were you cmployed          B. have you been employed C. had you been employed       D. will you be employed 答案：B 解析: 答语中的since1990是关键信息。对染色质和染色体的错误叙述是（ ）A．染色质是细胞核内易被碱性染料染成深色的物质B．染色质和染色体的形态结构、化学成分完全相同C．染色质或染色体的主要成分是DNA和蛋白质D．染色质或染色体只存在于真核细胞的细胞核中