Final answer:
Terms C, D, E, and F are true about vectors because they include both magnitude and direction, which are necessary to define a vector in physics.
Step-by-step explanation:
When we say a vector is true about vectors, we mean that it has both magnitude and direction. Looking at the options provided: A. 3N is a scalar since it lacks direction; B. 10 is also a scalar; C. 15<--- indicates magnitude and left direction, so it can be a vector; D. 30N, right has magnitude and direction, making it a vector; E. 26---> also shows magnitude and direction, qualifying as a vector; F. 10N, south has magnitude and a direction, which qualifies it as a vector. It's important to include both magnitude and direction when defining vectors in physics.