About 200,000 ____ (游客) came to Tai'er zhuang Ancient Town during May 1 holidays. It's difficult to believe.
玉米高茎对矮茎为显性,现在有高茎玉米进行自交,后代既有高茎又有矮茎,比例为3:1。令后代中全部高茎玉米再进行自由交配,则后代高、矮之比为
已知集合S={x|3x+a=0},如果1∈S,那么a的值为( )