The effectiveness of a constitution is determined by multiple factors, including the people who enact it, the substantive provisions within it, and the presence of a single institution with a monopoly of power. Let's examine each of these factors in detail:

1. People who enact the Constitution:
The individuals responsible for drafting and enacting a constitution play a crucial role in its effectiveness. If the process is inclusive, transparent, and representative of the diverse interests within a society, it is more likely to result in a constitution that is widely accepted and respected. The legitimacy of the constitution is enhanced when it is perceived as a product of a fair and inclusive process.

2. Substantive Provisions:
The substantive provisions of a constitution refer to the specific content and principles outlined within it. These provisions typically include fundamental rights and freedoms, the structure and powers of government institutions, the distribution of powers between different levels of government, and mechanisms for resolving conflicts. The effectiveness of the constitution depends on the clarity, comprehensiveness, and relevance of these provisions. A constitution that guarantees and protects individual rights, establishes a system of checks and balances, and provides mechanisms for peaceful resolution of disputes is more likely to be effective.

3. Single institution with monopoly of Power:
Having a single institution with a monopoly of power refers to a system where power is concentrated in the hands of one central authority. This can be a president, a monarch, or a ruling party. The effectiveness of a constitution may be influenced by the presence or absence of such a system. In some cases, a concentration of power can lead to authoritarianism, where the rights and freedoms of citizens are suppressed. On the other hand, a well-functioning single institution with a clear mandate and accountability mechanisms can ensure stability and effective governance.

In conclusion, the effectiveness of a constitution is determined by the people who enact it, the substantive provisions within it, and the presence or absence of a single institution with a monopoly of power. All of these factors are interconnected and contribute to the overall functioning and legitimacy of the constitution. Option 'C' is the correct answer as it includes both the people who enact the constitution (factor 1) and the substantive provisions (factor 2), which are essential for determining the effectiveness of a constitution.