【题目】Effective measures should and laws should be passed
to protect pandas. Otherwise, they are certain to die out.

【答案】e taken
【解析】句意：应该采取有效的措施，通过法律保护熊猫。否则，他们一定会灭绝。take measures 固定短语“采取措施”。easures与take搭配，用被动语态，情态动词后接动词原形，故填be taken。