The correct option is
B reason
The word, 'programme' is a noun which means '
a planned series of future events or performances'. The word, 'plan' is a noun which means 'a detailed proposal for doing or achieving something'.
The word, 'reason' is a noun which means 'cause/explanation'.
The word, 'greed' is a noun which means 'intense and selfish desire for something, especially wealth, power, or food'.
The appropriate word to fit the blank is 'reason'. The sentence, 'His love for money is the only reason that drives him to work so hard' means that 'The cause which drives him to work so hard, is his love for money'. Hence, option C is correct.
Given the meanings as above, Options A, B and D are incorrect as they cannot be used in the blank to make a meaningful sentence. Hence, these options are incorrect.