The correct idiom is "Consider X Y". "consider to be" is wrong in GMAT.
Let's look at the question.
A.Supporters of tax breaks that local governments award to businesses each year to prevent them from moving consider them vital economic development tools
-- second "them" incorrectly refers to businesses rather than to "tax breaks"
B.Supporters consider tax breaks that local governments award businesses each year to prevent them from moving to be vital economic development tools
-- "consider to be" is wrong.
C.Supporters of tax breaks that local governments award businesses each year to prevent them from moving consider them vital economic development tools
-- second "them" incorrectly refers to businesses rather than to "tax breaks"
D.Supporters consider tax breaks that local governments award businesses each year to prevent them from moving vital economic development tools
"that local ...." is a modifier for "tax breaks". consider "tax breaks" .... "vital economic development tools" consider X Y. CORRECT.
E.Supporters of tax breaks that local governments award businesses each year to prevent them from moving consider the tax breaks to be vital economic development tools
-- "consider to be" is wrong