Which of the following is wrong?

L$$tfen birini se$$in:

a$.2D$ bin packing problem is harder to solve than $1D$ bin packing problem

b$.$ Rounding does not guarantee the optimal solution

c$.$ The computation time and number of nodes have a linear relationship for traveling salesman problem

d$\mathrm{.}1$D bin packing problem is binary integer programming

e$.$The capacity of bins is important in bin packing problem