In Mollusca : 1. A soft and spongy layer of skin forms a mantle over the calcarious hump. 2. The space between the hump and the mantle is called the mantle cavity 3. In mantle cavityfeather like gills are present. Regarding 1,2 and 3:

Question

( a ) 3 is incorrect; 1 and 2 are correct
( b ) 1 is correct but 2 and 3 are incorrect
( c ) 1 is incorrect but 2 and 3 are correct
( d ) 2 is incorrect but 1 and 3 are correct