下列是人体中几种体液的正常pH，其中酸性最强的是（　　）

It's blue and yellow.     

阅读短文，判断正误。

    My dad works from Monday to Friday in a bank. He uses the computer to count money. His job is very important in the bank.

    Dad is also busy at home. At weekends he cooks dinner. Usually he cooks Italian food. On Sundays he makes five pieces of pizza. Sometimes he cooks chicken and makes Chinese food. My mum watches and helps him. I help my dad, too. I wash the dishes.

    Many people think it is strange for a man to cook. But my dad enjoys his hobby. Cooking relaxes him. He is a weekend cook.

方程x²+3x+1=0的两个根为α、β，则 $\sqrt{\frac{\alpha }{\beta }}$ + $\sqrt{\frac{\beta }{\alpha }}$ 的值为____．

有一种测量人体重的电子秤，其原理图如图所示，它主要由三部分构成：踏板、压力传感器R（是一个阻值可随压力大小而变化的电阻器）、显示体重的仪表G（实质是理想电流表），设踏板的质量可忽略不计，已知理想电流表的量程为3A，电源电动势为12V，内阻为2Ω，电阻R随压力变化的函数式为R=30-0．02F（F和R的单位分别是N和Ω）。下列说法正确是             （   ）