The description that will show that it is safe to perform inference is that (a) Both dotplots are roughly symmetric. There are no outliers in either dotplot.
In order to use the two-sample t procedure to make inferences, certain conditions need to be met such as the sample being random and independent.
The variances for the groups in the data need to be equal which is why the presence of no outliers in either dotplot would present an safe opportunity to be able to perform inferences on the data.
In conclusion, option A is correct.
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