题目

The popular belief has been challenged after a recent research ________ cartilage(软骨) in human joints can't repair itself. A . where B . whether C . when D . that 答案：D下列实例中属于不遗传的变异是（ ）A．普通甜椒的种子经过太空漫游后，培育出大而甜的“太空椒”B．高产易倒伏小麦与低产抗倒伏小麦杂交培育出高产抗倒伏小麦C．在毛色均表现正常的虎群中，出生了一只白色的幼虎D．干旱环境中异常矮小的玉米植株