The gateway reaction of aerobic respiration 
(i) Is also called link reaction  
(ii) Is catalyzed by pyruvate dehydrogenase complex 
(iii) Involves carboxylation and dehydrogenation 
(iv) Produces acetyl-CoA and reducing power 
Correct statements is/are 

The gateway reaction of aerobic respiration is indeed also called the link reaction. This reaction links glycolysis to the citric acid cycle (Krebs cycle).
The reaction is catalyzed by the pyruvate dehydrogenase complex, which converts pyruvate (a product of glycolysis) into acetyl-CoA.
However, the gateway reaction does not involve carboxylation. Instead, it involves the decarboxylation of pyruvate.
It also produces acetyl-CoA and reducing power in the form of NADH, but not through carboxylation.