The first seat can contain any person. After that person is seated, the next seat can contain any of the remaining people. Repeat. That's 8 times 7 times 6...ways...or just 8! (Eight factorial) = 8*7*6*5*3*2*1.
b) 4! Ways to order the couples2! Ways to order each couple24 * 2^4 = 24 * 16 = 384 ways
c) 2 ways to order the genders4! Ways to order each gender2 * 4! ^2 = 2 * 24^2 = 1152 ways.
Q2)
A straight can start with any of these cards, regardless of suit: A, 2, 3, 4, 5, 6, 7, 8, 9, ...