L3
讲座
1. What does the professor mainly discuss
A hypothesis that rivers formed before the rise of plant life
A study of the effects that rivers have on soil formation
A debate surrounding two opposing hypotheses
New evidence in support of a previously proposed hypothesis
2. What limitation of Cotter’s research does the professor mention
Cotter’s research findings could not be replicated.
Cotter’s research was based on one geographical area.
Cotter’s research did not take into account lateral accretion.
Cotter’s research did not account for changes in climate.
3. What did researchers try to confirm about rivers in a recent study
That rivers now have the same shape worldwide
That rivers were responsible for the spread of plant life
That a change in the shape of rivers is linked to the spread of plant life
That most rivers emerged during a specific geological time period
4. Why does the professor describe the composition of the sediment of the earliest
rivers
To identify the evidence used to determine how the rivers flowed
To explain why the rivers could easily dry out
To suggest that the sediment was once fine sand
To suggest that the geological record might be flawed
5. According to the professor, what is an effect of lateral accretion on a meandering
river
Bends in the river become gradually straighten B.
Material from one riverbank is deposited on the other.
The intensity of the river’s flow increases.
The growth of plants on the outer riverbank is enhanced.
6. Why does the professor say this:
To find out what the students know about Mars
To question certain geological studies of o ther planets
To express a reservation he has about the hypo thesis
To indicate that he is going to change the topic
