Haven't taken Computer Science in a year so my answer may be wrong (APCSA).
Defining Column B,
Selection is when a piece of code is run only when its conditions are met.
Iteration is typically represented by for loops, enhanced for loops, and while loops, and will all repeat until a condition is met.
Sequence is usually the simplest, carrying out commands in order.
From what I see, the first box in column A is a sequence as it defines and casts num1 and num2, computes its difference in int form, and prints it out. The second box in column A is a selection even though it counts to 5 in the first segment of code. The key here is the if else statement as it checks that num1 is greater than num2 before it subtracts. The third box in column A is an iteration due to its enhanced for loop.
Computers are just a bunch of different parts that work together to make a system function. All you need is a case a fan and a CPU, oh and some RAM. Obviously if you want it fully functional, you can look online but yes it's quite simple really!
