焊接常用的16Mn钢板材，当厚度大于30mm时，预热温度为100～150℃。( )
参考答案：对
FIDIC《施工合同条件》规定，承包商签订合同时应提供( )，接受预付款前应提供预付款担保。
A．留置担保 B．保证担保C．抵押担保 D．履约担保
He had to sell his luxury car, ________ his company was in debt.
A．before
B．until
C．while
D．for
