增加：在缺词处加一个漏字符号（∧），并在其下面写出该加的词。

删除：把多余的词用斜线（\）划掉。

修改：在错的词下划一横线，并在该词下面写出修改后的词。

注意：1).每处错误及其修改均仅限一词；

2).只允许修改10处，多者（从第11处起）不计分。

    My grandfather and I enjoy fishing.

    One Sunday morning we go fishing at a lake. We took ours fishing poles and headed for the lake. As soon as we arrived, so we dropped the lines into the water. Before waiting for about half an hour, I was beginning to get impatiently. I wanted to give up, and my grandfather told me to wait a little longer. Finally, there were a sudden pull at the pole and fish was caught. Within the next few minute, my grandfather also caught a fish.

    Felt hungry, we built a fire by the lake and barbecued the fish. It was delicious.

一个小组在实验时，用弹簧测力计在空气中测一个铁块的重是3.5N，当把这个铁块的一半浸在水中称时，弹簧测力计的示数是2.8N，则此时铁块受到的浮力是____；如果把这个铁块全部浸没在水中时，铁块受到的浮力应该是____，那么弹簧测力计的示数应该是____。