Which of the Following Is NOT One of the Three

Which of the following is NOT one of the three major assumptions that underpin the concept of a 'contract of employment'

A) that the relationship between employer and employee is an individual one, made between two parties of equal bargaining strength
B) that there is an imbalance of power between the two parties
C) it consists of a promise to work (or be available for work) for which payment is promised
D) since there has been a free exchange of promises, the two parties have reciprocal, but different rights and obligations