Answer:
A) Tankers can easily be redesigned so that their use entails less risk of an oil spill.
Step-by-step explanation:
The option that if true most seriously weakens the argument above is: tankers can easily be redesigned so that their use entails less risk of an oil spill because the statement says that importing oil on tankers entails a greater risk of an oil spill than offshore oil-drilling and the option chosen directly talks about that and says that the tankers can easily be redesigned to decrease the risks of an oil spill which goes against the argument given.
The other options are not right because the options B and C support the argument given. Also, options D and E doesn't talk about oil spill which is the topic on the argument presented.