A promise is defined as any agreement that yields an obligation. It is acceptable not to keep one' s promise if either the person to whom the promise is made tells the promisor not to keep it, or the promisor is unable to fulfill the obligation due to circumstances beyond the promisor' s control. Which one of the following is an application of the principle above pertaining to promising? ['Paul agreed to lend Tom $10. But Paul also owes Maria $10. So it is unacceptable for Paul to fulfill his promise to lend Tom $10 while he still owes Maria money.', 'Felicia agreed to tutor Alan in mathematics on Tuesday. However, on his way to the tutorial session, Alan was injured in a car accident and was unable to attend that day. Thus, it was acceptable for Felicia not to tutor Alan in mathematics on Tuesday.', "Quinn agreed to water Laura's plants while Laura was out of town. But Laura had forgotten to give Quinn the keys to her place. However, it was unacceptable for Quinn to fail to fulfill his promise to Laura, since Laura did not excuse Quinn from his obligation to water her plants.", 'Ian agreed to pick up Ali at the train station. But Ian decided to stop and return his overdue library books first. As a result, Ian was unable to pick up Ali at the train station. Thus, it was acceptable for Ian to fail to pick up Ali at the train station.']