用七条直线最多可画出几个不重叠的三角形( )
A．10个 B．11个C．12个 D．13个
参考答案：B
Frank, with his two sisters, ________ London by train which ________at 8:30 next morning.
A．is leaving for; will leave
B．are leaving for; leaves
C．is leaving for; leaves
D．will leave for; will leave
入炉空气量太小，则炉膛（），火焰呈暗红色。
A、发暗
B、发红
C、发亮
D、发出轰轰声
