NO.PZ2023091802000177
问题如下：
In late June, John
purchased two December gold futures contracts. Each contract size is 5,000
ounces of silver and the futures price on the date of purchase was USD 18.62
per ounce. The required initial margin is USD 6,000 and a maintenance margin of
USD 4,500. You are given the following price history for the December silver
futures:
On which days did John receive a margin call?
选项：
A.July 1 only
B.July 1 and July 2 only
C.July 1, July 2 and July 7 only
D.July 1, July 2 and July 8 only
解释：
如题
