U.S.officials, including the number-two American commander here, Army Lieutenant General Charles Jacoby, say such occasional spectacular attacks are,in a way, evidence of the decline of al-Qaida in Iraq, which once staged dozens of attacks every day.

VOA: standard.2009.12.11

In the first place, a mask is nearly always occasional.

首先，这个节目几乎是偶然的。

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