2. (from SW) Consider the IV regression model: Y_{i}=\beta_{0}+\beta_{1} X_{i}+\rho_{2} W_{i}+u_{i} where X; is endogenous, W; is exogenous, and Z¡ is an instrument for Xị. Suppose that thefirst three assumptions for TSLS are satisfied. Which TSLS assumption is not satisfied when: a) Z; is independent of (Y;, X;, W;) b) Z; = W; c) W; = 1 for all i d) Z¡ = X¡.

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