Consider the statements given below and select the correct statements :

(A) A secular trend is a short trend.

(B) In a free hand curve method; the area above the trend line should be greater than the area below it.

(C) The trend line obtained on the basis of least squares is known as the line of best fit.

(D) When a data is a collection of one or more variables at same point of time it is called cross-sectional data.

(E) For the equation of a straight line trend $y_c= a+bx ,$ values of a and b can be fund using $a=\frac{∑y}{n}$ and $b=\frac{∑xy}{∑x^2}$

Choose the correct answer from the options given below :

(C), (D) and (E) only