She pretended _______ me when I passed by.
A:not to see
B:not seeing
C:to not see
D:having not seen
一个四位数,使它恰好得等于两个相同自然数的乘积,则这个四位数是____ .
— He seemed interested in my experience, but he didn't ask for references.
如图所示,在一块平板玻璃上放置一平凸薄透镜,在两者之间形成厚度不均匀的空气膜,让一束单一波长的光垂直入射到 该装置上,结果在上方观察到如图所示的同心内疏外密的圆环状干涉条纹,称为牛顿环,以下说法正确的是( )