The subject that will help you most vary's from person to person. What field do you want to work in? What knowledge is required? For instance, I would like to be a programmer. That requires programming knowledge in Programming and Scripting languages such as Python, Java, Batch, Bash, Lua, C#, C++, and much more, I don't need to know them all, but it helps to know a few. It helps if I have a degree in Computer Science & have a creative view over things. Or I could be an engineer requiring math and a whole plethora of different things. What you need is based off of what you want. You can find websites that will give you more information and such things, but <u>DO WHAT YOU WANT TO DO</u>.
Lieutenant is not a part of the main clause, and it is an address to a person that is inserted into the sentence. It must be therefore separated by comas on both sides: the correct answer is a.
