True or false, an implicitly unwrapped optional variable must have an exclamation mark affixed after it every time it is used. 答案选项组

When keyboarding, if you want to be fast and accurate you should return your hands on home row with your fingers relaxed and your eyes on the text use only your index fingers to hunt and peck keep your fingers stiff and your eyes on the keys slouch in your chair and keep your fingers hovering over all of the keys

What makes myhexadecimalnumber a child of mynumber? which methods does myhexadecimalnumber inherit directly from the mynumber class? what can an instance of the mynumber class do? what can an instance of the myhexadecimalnumber class do? which methods are overridden? why are they overridden? how many examples of overloading are there? why was this done? where is the super keyword used? what is it doing? why isn’t the incoming value set immediately in the second myhexadecimalnumber constructor? how many examples can you find of an inherited method being called?

Description: write function lastfirst() that takes one argument—a list of strings of the format "lastname, firstname" —and returns a list consisting of two lists: (a) a list of all the last names (b) a list of all the first names