An experiment consists of eight steps - H, J, K, L, M, O, P, and S - that all must be performed. Three days are allotted for the experiment. Each step requires exactly one morning or else one afternoon to be performed, and at most two steps can be performed during any given morning or afternoon. The following restrictions must be observed: J must be performed on the second day. P must be performed in the morning. K and M must be performed at the same time. J must be performed at some time after M has been completed and at some time after O has been completed. O must be completed at some time before P and at some time before S. Which of the following must be completed at some time before J?
Explanation: Given the constraints: J must be performed after M is completed, and J must be performed after O is completed. K and M must be performed at the same time. Since K and M are simultaneous, and M must be before J, it logically follows that K must also be completed before J.
