5)
The premise is that SUV are subject to only a small fraction of the safety standards the government imposes on ordinarly passenger cars.
The conclusion is that therefore, in a high-impact collision, SUV passengers are more likely to be injured.
5 says that the higher probability of SUV passengers be harmed may be due to some cause ( false sense of security ) other than SUVs' "non-compliance" to government standards. This may weaken the argument, or at least, not strenghten it by giving an alternative explanation.
4 does somewhat strenghten the argument. If SUVs are
bulkier, then their manoeuverability can be reduced. Also, if the acceleration is hindered, then the ability to avoid such a collision (by quickly bifurcating elsewhere before the impact), may be hindered as well. Agree, that this is more inference but IMO, it could strenghten the argument more than 5 does.
1 is no good because it clearly strenghtens the argument by saying that because SUV car makers are not under the same safety standards, then they will no be inclined to make their cars safe ( they don't have to )