When the concentration of A is doubled, the rate for the reaction: $2\mathrm{A}+\mathrm{B}\to 2\mathrm{C}$ quadruples. When the concentration of B is doubled the rate remains the same. Which mechanism below is/are not consistent with the experimental observations? 

Step I : 2A $\rightleftharpoons$D ( fast equilibrium)

Step II :B+D $\to$E(slow)
Step III :E $\to$2C (fast)

Step I :A+ B$\rightleftharpoons$ D (fast equilibrium)
Step II :A +D$\to$2C (slow)

Step I :A+B$\to$ D (slow)
Step II :A+D $\to$2C (fast equilibrium)

Step I : 2A$\to$ D (slow)
Step II :B+D $\to$E (fast)
Step III :E$\to$ 2C (fast)