Rate of catalytic hydrogenation of alkenes
Catalytic hydrogenation is more or less a surface phenomenon so sterics play the deciding role in the rate of hydrogenation.   

From Wikipedia:


  


Here's a newman projection of the three Alkenes.


 A = cis-dimethylbutene, B = trans-dimethylbutene, C = 2-methylpropene

From here it is easy to see that the cis-dimethylbutene will have the least hindered approach towards the surface of the catalyst as both the methyl groups can be made to face away from the surface.   

The rates of hydrogenation in the case of trans-dimethylbutene and 2-methylpropene will be decided by which one of them is more strained.  


     


2-methylpropene is more strained than trans-dimethylbutene.  

So, we can now establish the order.  

$$\text{A &gt; C &gt; B}$$



References   


Catalytic Hydrogenation:A Core Technology In Synthesis; Ryoji Noyori  
Wikipedia article on Hydrogenation