is father sitting not far from him."Dad, how did you get back so early" Tang Wulin looked at Tang Ziruan in surprise.Tang Ziran smiled faintly: "It's getting late, it's dark. You've already learned me...e on mecha manufacturing principles. Tang Wulin had little exposure to this area of knowledge before, so he listened very attentively. 。Please vote for me and recommend me! 。To be continued... 。 420...