In the following passage some of the words have been left out.Read the passage carefully and choose the correct answer for the given blank out of the four alternatives.
Passage:

We have rich cultural _____ . Its roots go into _____. Ours has never been a closed ______. It has _______ just like a tree, ______ to external ______ but holding its roots _______. But one wonders today whether it will be able to hold its _____. The ______ of our cultural heritage has come under the _____ of western culture.