1) is not true. straight lines are not always functions, because for a line to be a function, it must pass the "vertical line" test. x = 1, for example, is a vertical line, and it does NOT pass the vertical line test, but it IS a straight line. this example shows that the first is false.
2) doesn't look like the complete choice, but if it's asking whether or not y = 2x + 1 is a function, the answer is yes. you can know this by plugging it into a grapher and seeing that it's a line that passes the vertical line test (aka, making it a function).