The graph below shows the reaction rates obtained when the irreversible, liquid$-$

L$21-23$

phase, catalytic reaction $AB$ was carried out in a PBR using the indicated catalyst $d_p,T,$ and $F_{T0}*C_{A0}$ was the same in each trial.

$*$FT$0=4000mo\frac{l}{h},T=400K$

$+FT0=4000mo\frac{l}{h},T=300K$

diamondFT$0=3500mo\frac{l}{h},T=400K$

OFT$0=3500mo\frac{l}{h},T=300K$

$$FT$0=1000mo\frac{l}{h},T=400K$

FT$0=1500mo\frac{l}{h},T=400K$

$diamon{d}_{FT0}=2000mo\frac{l}{h},T=400K$

Which, if any, of the conditions shown $($flow rates, $T,$ and $d_p)$ is the reaction limited by external diffusion?