Among the following statements which are correct?(a) Historical method is a complex process involving the search for sources of information, its critical evaluation, synthesis and exposition(b) Reasoning should be done if the basis of the proposition is merely conjuncture(c) The cult of 'document' especially the "official document" owes its development largely to Leopold Von Ranke(d) Oswald Spengler's philosophy of history opens with a vehement attack on the European periodization of history into ancient, medieval and modern.Choose the correct answer from the options given below:

• A. (a), (b) and (c) only
• B. (a), (c) and (d) only
• C. (b), (c) and (d) only
• D. (a) and (b) only