If Brazilian industry is successful in producing submarines and stealth corvettes, demand for Brazilian military hardware will only grow (...). Of concern, however, are Brazil's long-term intentions with regard to the construction of BNS Alvaro Alberto. (...) It will be necessary to keep a very close eye on the Brazilian shipbuilding and nuclear industries in the 2030s, especially as domestic demand for this class of vessel is satisfied.

A preposição que segue o adjetivo "successful" é "in".  A preposição que segue o verbo "regard' é "to" Ex: And I would say the same with regard to private medicine.( E eu diria o mesmo em relação à medicina privada.)
"Keep an eye"- é seguido da preposição "on" Ex: 
Would you keep an eye on my son for me while I am gone? (Você pode ficar de olho no meu filho enquanto eu estiver fora?)
Gabarito do Professor: C

successful in

with regard to/on

close eye on