题目如下：好像是2002年的一个真题。
Company B makes a bid for company A at $15 per share.
A merger arbitrage manager acquires a long position in A and a short position in B.
When constructing the variance-covariance matrix for the var calculation,which of the following is the best choice when computing the volatilies and correlations?

A:EWMA volatility, EWMA correlation
B:EWMA volatility, Equal weight correlaion
C:Equal weight volatility,  EWMA correlation
D:Equal weight volatility,  Equal weight correlaion