30. According to the passage, who are Wadsworth and Sherby?
(A)They are metallurgical historians revealing the background of producing Damascus swords.
(B)They are metallurgists at Stanford University attempting to produce durable or plastic steel.
(C) They are warriors in modern America, who still used Damascus swords in daily-life business.
(D) They are crusaders of metallurgy trying to discover ways of making better weapons.