L4：
讲座
1. What is the lecture mainly about?
New technologies for mining natural gas on the ocean floor
Evidence that natural gas is safer than other fossil fuels
A possible source of natural gas
The similarities between natural gas and other fossil fuels
2. According to the professor, what are two ways in which natural gas is preferable to oil and other fossil fuels?（多选题）
It can be extracted more easily.
It bums more cleanly.
It is more versatile.
It is s afer to transport.
3. What does the professor imply about supplies of natural gas?
Supplies might be larger than previously thought.
Supplies may eventually be replaced by other fossil fuels.
Supplies are being depleted more quickly than predicted.
Supplies should not be used as a main source of energy.
4. According to the professor, what could happen to methane hydrate crystals during an underwater landslide?
The crystals might sink to the bottom of the ocean.
The crystals might scatter across the ocean floor.
The crystals might break down and release methane gas.
The crystals might cause sediments to solidify.
5. What is the professor’s opinion about the effect of global warming on methane hydrates?
Methane hydrates could become more abundant sediments on the ocean floor.
Methane hydrates could become more difficult to extract.
Methane hydrates could disappear from the earth except the Arctic.
Methane hydrates could become dangerous even if humans do not try to extract them.
6. What does the professor imply when he says this:
The class does not need to talk about what the student just said.
Geology students sometimes must be willing to work in unpleasant environments.
He is surprised that the class finds the student’s comment amusing.
He wants to suggest a solution to the problem the student just raised.
