under discussion 和in disscussion 的区别

under和at和in和on的区别 in the water 和 under the water 的区别? under the snow和in the snow 的区别 in the sun和under the sun的区别 帮俺做道题His ideas___the topic under discussion in the meeting. in control 和under control区别? talk about 和 have a discussion的区别 below和under的区别 under control,in control (of)的区别 under和below 和down的区别 in the charge of 和under the charge of 的区别 in the guise of和under the guise of 的区别?