题目

 No one knows ______how the universe began, however, some scientists believe it began with ‘a big bang’. A. exactly           B. extremely               C. generally               D. gradually 答案：A做馒头时要在发酵好的面团中加食用碱，以便产生气体使馒头疏松多孔，面团在发酵过程中产生的物质的酸碱性是（   ）A．酸性B．碱性C．中性D．无法判断