Where is the Start Frame Delimiter (SFD) found in an ethernet frame?

Fast answer i need for apex ! smartphones should be banned from the classroom in public schools so that students cannot cheat on test so easily? which is an example of a counter argument to the thesis above? a.the classroom is a place for learning not for making phone calls b. smartphones are useful learning tools in the modern classroom c.banning smartphones will not students pay attention to teachers any better d. banning smartphones would decreased incidents of theft