It's seven o'clock in the morning. It's time for breakfast. Jenny's mother is cooking in the kitchen. Jenny would like some milk and bread. Li Ming would like some eggs, bread and juice. After breakfast, Jenny and Li Ming will go to school by bike.

不等式$4^x+2^{x+1}-k>0$对$x\in R$恒成立，则k的取值范围是（    ）

硅单质及其化合物应用很广。请回答下列问题：