I would select Straight 2-way Merge sort over Quick sort when which of the following are true. A. Incorrect selections will be penalized.
B. If I knew that the distribution of the data was significantly skewed.
C. If space were not an issue If I knew the size of the data set was very large.
D. If I knew that the data tended to be in order.

I would select Straight 2-way Merge sort over Quicksort when:

C. If space were not an issue If I knew the size of the data set was very large.

Explanation:

For large datasets, the Straight 2-way Merge sort has been found to be more efficient than the Quicksort.  It also works faster than Quicksort.  However, Quicksort has been found to be more efficient, working faster than the Straight 2-way Merge sort with small datasets.  The two are algorithms for sorting.  While Straight 2-way Merge Sort uses two streams with repetitions, the Quicksort uses just one stream without repetitions and additional storage space.

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