STIMULUS - The first line of the stimulus starts off by presenting some facts about taxes on goods that come in a country (can be said as import tax). The second sentence of the passage forms a conclusion based on the above information (i.e. the information present in the first sentence).
TYPE OF QUESTION (as understood from the question statement) - Weaken
PRE-THINKING - the conclusion tries to make a connection between the taxes and the transportation costs, with no clear connection between the two - maybe the two are not related.
OPTIONS - A: The factors mentioned might not be 'all' the factors affecting but maybe 'some' of the factors affecting how transported goods are taxed. Thus, this option does not weaken the statement to a huge extent.
B: Irrelevant. It does not matter how goods in other countries are taxed. This option does not present any information that can help weaken the conclusion or affect it in any way.
C: This is somewhat in line with our pre-thinking. If the transportation costs do not include taxes levied on goods shipped into this country from overseas, then the businesses do not need to carefully figure these factors into any estimation of transportation costs. This helps weaken the conclusion and is the answer.
D: As mentioned in the understanding of the STIMULUS - we are talking about import taxes and it does not matter if export taxes do not depend on one of the factors mentioned.
E: Irrelevant. It does not matter if new businesses underestimate transportation costs. It does not affect our conclusion.
ANSWER: C