A constitutional government by definition is a

(a) Government by legislature — Incorrect. A constitutional government is not defined by legislative supremacy; powers are structured and limited by the Constitution.
(b) Popular government — Incorrect. It may be democratic, but constitutional government specifically means government under constitutional limits, not merely rule based on popular will.
(c) Multi-party government — Incorrect. A multi-party system is a party arrangement, not the defining feature of constitutional government.
(d) Limited government — Correct. By definition, constitutional government is limited government, where authority is restrained by the Constitution, rule of law, and checks and balances.