Which of the Following Are Included in Calculating Weighted Average $\quad$

Which of the following are included in calculating weighted average number of shares used for basic earnings per share:
I $\quad$ an adjustment for the date on which new shares were issued
II $\quad$ the date on which shares acquired under a share buyback were acquired by the company
III $\quad$ the amount paid up on shares
IV $\quad$ the number of shares on issue at the beginning of the reporting period

A) I and II only
B) each of I, II, III and IV
C) I, II and IV only
D) III and IV only