—How was your recent trip to Sichuan?

—I've never had ________ one before.

A．a pleasant

B．a more pleasant

C．a most pleasant

D．the most pleasant

管子焊口焊后进行热处理时，加热宽度从焊口焊缝中心起每侧不少于焊缝宽度（）倍，且不少于（）毫米。