Which of the Following Statements Is True Concerning VAR Impulse $\pm$

Which of the following statements is true concerning VAR impulse response functions?
(I) Impulse responses help the researcher to investigate the interactions between the variables in the VAR.
(ii) An impulse response analysis is where we examine the effects of applying unit shocks to all of the variables at the same time.
(iii) Impulse responses involve calculating the proportion of the total forecast error variance of a given variable is explained by innovations to each variable.
(iv) If the $\pm$ 2 standard error bars around the impulse responses for a given lag span (i.e. include) the x-axis, it would be said that the response is statistically significant.

A) (i) , (ii) , (iii) , and (iv)
B) (i) , (ii) and (iii) only
C) (i) only
D) (i) and (ii) only