tigerszheng

The author uses an analogy to get his conclusion.

So, in order to support his conclusion, we should find the similariy between thw two things.

The similarity is knitting needles are known to cause injury and death just like the hypodermic.

Is it right?

Please check.

tigerszheng

It says :  they CAN be lethal.

If they have been known to be lethal (that is, we proved that they are lethal), the conclusion is supported.

Please check...