Would you expect cross-price elasticity between the following pairs of products to be positive, negative, or zero?

Question:

Would you expect cross-price elasticity between the following pairs of products to be positive, negative, or zero?
a. Television sets and DVRs
b. Rye bread and whole wheat bread
c. Construction of residential housing and furniture
d. Breakfast cereal and men's shirts
Explain the relationship between each pair of products.