Which Assumptions Are Required in Using the Simple Linear Regression $y _ { i } = \beta _ { 0 } + \beta _ { 1 } x _ { i } + \hat { I } _ { 1 }$

Which assumptions are required in using the simple linear regression model $y _ { i } = \beta _ { 0 } + \beta _ { 1 } x _ { i } + \hat { I } _ { 1 }$ ?