单项选择题
A．since the last century B．for a very long time C．since a few hundred years ago D．since a few years ago
A．an equal amount of silver B．an equal amount of gold C．all the water in the jar now D．the water that leaves the jar
A．Archimedes took a bath B．Archimedes discovered his principle C．The king of Syracuse asked him to sovle a problem D．Archimedes did the experiment on his crownA. c;a;b;dB.b;c;a;dC. b;c;d;aD. c;a;d;b