The manufacturer and customers remain the same, only the model of engine has been changed for the better. New safety features have been added. Logically , the sales of new engine should be more than for old engine type. But what happened was opposite of this. On the basis of this , the engine maker concludes that perhaps the customers themselves don't bother about safety, because otherwise they would have bought more of new engine type.
We are asked to find a weaken option choice for this conclusion drawn by the engine maker. I am trying to think what actually motivates the customer to still buy the the old type engine. Can there be any other factor which the passage has not mentioned. Or may be the sales data itself has some or the other logical flaw which we do not know of. Ideally I must not argue against what is given, but if I see there is a process error done by the sales analyst team and they by mistake got wrong figures, then obviously such a conclusion cannot be drawn.
Moving to the options :
1) Both private and commercial airlines are the customers of this engine maker. But are we told anything else here. Who the customer is doesn't tell us why the customers bought less of new engine type, specifically because we again lack more information here. Incorrect choice.
2) This option tells us about one mindset factor of the customers which actually might have led them to believe and trust more the old engine type. If this is the case, can we say then that the customers were not safety conscious... I don't think so we can now say that strongly.. perhaps they actually are safety conscious, that is why they are bothering to buy old engine type only . This option choice weakens the conclusion . A possible correct choice.
3) This option seems to add weight to the conclusion. If many customers actually bought from other engine makers who did not increase safety features, then we again have a doubt on the customers behavior. Perhaps they are in real less safety conscious as the engine maker has concluded. Incorrect choice.
4) This option choice actually rules out a possible reason for not choosing new engine type. The plane engines currently in use by the customers can be easily changed to the new type. So, a customer cannot make that excuse for not buying new type engine. This actually adds more weight to the conclusion. Incorrect choice.
5) This option choice again rules out one factor for not choosing new engine type - the factor of cost. If the new engine type was way too costly than old engine type, a customer could make that excuse for not buying the new type engine. In that case, it would have been difficult to mask the customer as less safety conscious. But now we know that this is not the case. Hence incorrect choice.
Answer should be B.