Final answer:
The degree of a polynomial is determined by the highest power of the variable, and the number of terms is determined by the distinct parts separated by addition or subtraction signs.
Step-by-step explanation:
A polynomial is an algebraic expression that consists of variables and constants combined using addition, subtraction, and multiplication operations. The degree of a polynomial is determined by the highest power of the variable. In the given expression, x + 5x - 2x^2 + 3x, the highest power of the variable x is 2, so the polynomial has a degree of 2. To find the number of terms, we count the distinct parts separated by addition or subtraction signs. In this case, there are four terms: x, 5x, -2x^2, and 3x. Therefore, the answer is B. 4.