根据
物体放在一凸透镜前30cm处，得到放大2倍的实像，则该凸透镜的焦距是____cm．
物体放在一凸透镜前30cm处，得到放大2倍的实像，则该凸透镜的焦距是\_\_\_\_cm．
在用单摆测定重力加速度实验中，用游标为20分度的游标卡尺测量摆球的直径，示数如图6所示，读数为____cm．用悬线的长度加摆球的直径作为摆长，代入单摆周期公式计算得到的重力加速度值____（选填“偏大”“偏小”或“不变”）．图6
在用单摆测定重力加速度实验中，用游标为20分度的游标卡尺测量摆球的直径，示数如图6所示，读数为\_\_\_\_cm．用悬线的长度加摆球的直径作为摆长，代入单摆周期公式计算得到的重力加速度值\_\_\_\_（选填“偏大”“偏小”或“不变”）．图6
From the passage, we learn that _____.
From the passage, we learn that \_\_\_\__.
Which of the following is probably the best title for this passage?
Which of the following is probably the best title for this passage?
The word “tip” in Paragraph 1 probably means _____.
The word “tip” in Paragraph 1 probably means \_\_\_\__.
The estimated sale value of the first note is about _____.
The estimated sale value of the first note is about \_\_\_\__.