The process $2 \mathrm{A}+\mathrm{B}\to \mathrm{C}$ taking place in two steps :
step 1 : 2A $\to \mathrm{D}$ and step2 : $\mathrm{D}+\mathrm{B}\to \mathrm{C}$ (slow), then rate of reaction gets

doubled when  [B]  is doubled
 

quadrapled when  [a] is doubled

doubled when  [a] is doubled
 

doubled when [B] is halved