Which of the following best explains why punch-card voting is no longer legal?

"Hanging chad"--The punch cards require a voter to punch a hole through their vote choice. 

This type of voting card got a lot of attention in the 2000 election when, in a recount in Florida, people could not tell if votes were for a person or not due to punches not being all the way through. If the hole is not punched all the way through, the piece of paper, the chad, hangs on leaving counters unsure if it was a mistake or intentional vote. Most states now have electronic forms like standardized testing.