Option A is partially correct here. The Option D is more appropriate and is therefore the correct answer.
Option B is incorrect as Preamble is a part of the Constitution (Kesavanand Bharti Case, LIC Case)
Option C is incorrect as in the 1995 case of Union Government Vs LIC of India also, the Supreme Court has held that Preamble is the integral part of the Constitution but is not directly enforceable in a court of justice in India.
Option D is correct as the preamble is of considerable legal significance in so far as it embodies an enacting clause.