Answer:
C) The invisible hand
Explanation:
Daniel here seeking to produce and increase his welfare is "led by an invisible hand" to negotiate with his suppliers and to sell goods to his neighbors in a way that everybody is better off as a result from these transactions.
This is also a clear example to what Adam Smith was referring to the invisible hand:
"in such a manner as its produce may be of the greatest value, he intends only his own gain, and he is in this, as in many other cases, led by an invisible hand to promote an end which was no part of his intention. Nor is it always the worse for the society that it was not part of it. By pursuing his own interest he frequently promotes that of the society more effectually than when he really intends to promote it. " Adam Smith, The Wealth of Nations, Book 4, Chapter 2