Over the past 20 years the once-sleepy fishing village ______ into an international tourism destination, with many visitors coming to explore its spectacular rainforests and beaches．

A．was transformed

B．was transferred

C．has been transformed

D．has been transferred

在寒冷天气进行焊接工作，水封安全器的外壳可用（）包上，或使用氯化钠或氯化钙水溶液。低压水封安全器的乙炔导管下端，应比安全管下端为（），以便发生回火时使爆炸气体经安全管排入大气中，而不致侵入乙炔发生器。