Alcohol seriously impairs an operator's judgment, which in turn poses a threat to the entire team's safety.

Why does "which" not refer to the noun "alcohol", why does it refer to the whole sentence "Alcohol seriously impairs an operator's judgment"?

so the word Furthermore in question one isn't considered a conclusion word

I struggled with question 5. I think the premise through me off.

can someone explain why these two sentences are part of the premise and not support.

Gerald cannot distinguish between green and brown.

By dividing its attention between its freight and commuter customers, a railroad serves neither particularly well.

premise Not every mammal is a good pet.

Support Because…your pet tiger is going to maul your face.

Conclusion Clearly mammals can't be considered good pets.

a couple analogous arguments

The trash bin in the kitchen is toppled and its contents, including some leftover salmon from dinner, spilled. Mr. Fat Cat is perched on the counter, self-satisfied, licking his paws. He knows his home well and is always in various rooms of the house as he is considered by his family the heart of their home. My hypothesis is that Mr. Fat Cat did not topple over the dinner because he knows his surroundings well and many cats lick their paws while comfortably at home. 

Law Students at harvard receive high dollar scholarships. Those who have received high grades in their undergraduate studies can receive them. All other scholarship recipients must receive nearly perfect lsat scores. Jim is a high dollar scholarship recipient. He though never received top grades during his undergraduate studies. Therefore Jim must have aced his lsat test.