Hi Josh,

I hope through your process of elimination you crossed off answer choices B and C because they included cell lines in the answers instead of antibodies. This leaves answer choices A vs D for you to pick from.

The question asks you to infer which treatment protocol will be highly effective in treating lung cell carcinomas. From the question stem, there is no indication that the cells that are part of these lung carcinomas are resistant. Therefore, you would start off with just using Ctx alone to see the response. There are several lung cancer cell types, so perhaps for the cells of these carcinomas Ctx is more effective than a combined treatment. If we're basing our logic on figure 1, we can tell that in non-resistant cells (like HP), there doesn't seem to be any significant differences in using Ctx vs Ctx + U3-1287. Therefore it would be better to use just Ctx, from a clinical standpoint to reduce the side effects of using a combined therapy.

Once you use Ctx you can see IF there are populations of resistant cells in the carcinomas and then proceed to use Ctx + U3-1287 for a more effective treatment for those cell types. If you start with Ctx + U3-1287 you don't know what cell groups you've targeted and there doesn't seem to be room to grow (at least from the context of the passage).

I hope this helps :)

- Shin