Final answer:
The Confederate navy secretary called upon ironclad warships to defeat the blockade, and the Merrimac (CSS Virginia) had 10 guns.
Step-by-step explanation:
The secret weapon that the Confederate navy secretary called upon to defeat the Union naval blockade was a) Ironclad warships. The Merrimac, also known as the CSS Virginia, had b) 10 guns. Confederate hopes were raised with the advent of ironclads like the CSS Virginia, which were armored and designed to challenge the Union's naval power. However, it is important to note that overall, the Confederacy did not have a strong navy, which was one of its weaknesses during the Civil War.