【单选题】

Our generation has made such immense discoveries and achieved undreamed enrichments of the outside of life, that it has lost touch with the inside of life. It has forgotten the true riches and beauties of its spiritual inheritance: riches and beauties that go far beyond our modern chatter about values and ideals. The mind’s search for more breadth has obscured the heart’s craving for more depth. Once again man has become the dupe of his own cleverness.And because it is difficult to attend to more than a few things at a time, we leave out a great range of experiences which comes in by another route and tells us of another kind of life. Our interest rushes out to the farthest limits of the universe, but we seldom take a sounding of the ocean beneath our restless keels. We get, therefore, a queer feeling that we are leaving something out. Knowledge has grown; but wisdom, savoring the deep wonder and mystery of life, lingers far behinD、Thus the life of the human spirit, which ought to maintain a balance between the world visible and the world invisible, is thrown out of gear.

From the passage we can most safely conclude that the author believes that ______ .
A、man should never be contented with what he has achieved
B．man is too concerned with things of the spirit
C．knowledge only will help maintain a balance between mind and heart
D．the soul of man is restless