Instead of beefing about what Mrs Martin has not done, her critics might take a look at what she is trying to do.批评者不要老是抱怨马丁太太没有做什么事情，不妨看看她正要做什么事情。Allow about eight hours for the drive from Calais. Alternatively, you can...
the many isotopes of carbon碳的诸多同位素Tritium is one of the mildest radioactive isotopes.氚是最和缓的放射性同位素之一.The inferno spewed a deadly plume of radioactive isotopes into the atmosphere.这个象炼狱般的地方将一缕致死的放射性同位素喷入大气层....