What is the unit digit of \((1! + 2! + 3! + 4!)\)?
Answer: B
We calculate the values of the factorials: \(1! = 1\), \(2! = 2\), \(3! = 6\), \(4! = 24\). The sum is \(1+2+6+24=33\). The unit digit of the sum is 3.