Answer:
d. cultural
Explanation:
Cultural barrier -
It is the expectation or rule according to any culture which prevents someone for any other culture from being included .
The most common cultural barriers are the religion and language .
Same is the case with Dave Malloy , as he treated the with a hearty handshake , but did not get a warm or good regards from the other person .
Because for each and every cultural and religion , the method of welcoming someone is different , hence , the case given in the question is of cultural barrier .