An ubiquitous virus, encephalomyocarditis , has been demonstrated upon occasion to affect swine.

曾经证实一种到处有的病毒-脑心脊炎病毒 -- 偶尔侵害猪.

辞典例句

You can be somewhat reserved and self - centred, and show great obstinacy upon occasion.

你可能有点拘谨和 自我 中心的, 必要时会非常顽固.

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