测试视网膜功能的方法简单而且安全。
There are also simple and safe ways to test the retina's functioning.
不过，在我们确切地了解雷公藤提取物有效而且安全之前，还需要进行更多的研究。
But more research needs to be done before we know for certain that TwHF extract works and is safe.
住在这幢坚固、舒适而且安全的住宅里的人，不禁对自己的成就自我陶醉起来。
The inhabitants of this solid, healthy, and secure dwelling, could not but be charmed with their work.
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