No computer will ever be able to do everything that some human minds can do, for there are some problems that cannot be solved by following any set of mechanically applicable rules. Yet computers can only solve problems by following some set of mechanically applicable rules.
Which one of the following is an assumption on which the argument depends

A．At least one problem solvable by following some set of mechanically applicable rules is not solvable by any human mind.

B．At least one problem not solvable by following any set of mechanically applicable rules is solvable by at least one human mind.

C．At least one problem solvable by following some set of mechanically applicable rules is solvable by every human mind.

D．Every problem that is solvable by following more than one set of mechanically applicable rules is solvable by almost every human mind.

E．(E) Every problem that is solvable by following at least one set of mechanically applicable rules is solvable by at least one human mind.

玉米是雌雄同株的植物，顶生的垂花是雄花序，侧生的穗是雌花序。已知玉米中有两对独立遗传的基因（T对t，B对b）可以改变玉米的性别，即把雌雄同株转变为雌株或雄株。当基因b纯合且t不纯合时，使植株没有雌花序成为雄株；当基因t纯合时，使垂花序为雌花序，不产生花粉，如图所示。

雄株的基因型为（），雌株的基因 型有（）种。