Comrade Li ________ be in Beijing because I saw him in town only a few minutes ago.
农业的社会主义改造中，高级社具有 _________性质。
How long ________ they ________ (dig) the ditch?
中国民族资产阶级在社会主义改造时期具有的两面性是指 _____。
She ________ her nervousness to the importance of the interview.
在点（0，-1）处的切线方程为 ________.
