Maintenance activities include ______.
①making enhancements to software products
②developing a new software product
③correcting problems
④adapting products to new environments

单项选择题The basic unit of measure in a computer system is the ______. It is the smallest unit in computing. There are some other measures in a computer, such as Kilobyte, Megabyte, Gigabyte and so on.

单项选择题When a bridge transmits an Ethernet frame, the Ethernet frame has ______.