选择相对应的答句

____What's your father's job?                                     A. Eleven.

____Who are they?                                                        B. They are my parents.

____How many people are there in your family?          C. He's a doctor.

____Who's this woman?                                                D. Yes, he is.

____Is this your uncle?                                                   E. She's my aunt.

Is your father ____(严格的）？

学完“浮力”知识后，小芳同学进行了相关的实践活动．（ρ_水=1.0×10³kg/m³）

（1）她选取一质量为750g、体积为1250cm³长方体木块，让它漂浮在水面上，如图甲所示．求木块受到的浮力．

（2）取来规格相同由合金材料制成的螺母若干，每只螺母质量为50g，将螺母逐个放置在漂浮的木块上．问：放多少只螺母时，木块刚好浸没在水中？

（3）她又用弹簧测力计、一只螺母做了如图乙所示的实验，弹簧测力计静止时的示数为0.4N．求合金材料的密度．