To solve this question, we need to evaluate each statement regarding the causes of errors in current transformers and determine which set of statements is correct.

1. Leakage Reactance in Secondary Winding Contributes to Ratio Error (Statement i): Leakage reactance in the secondary winding does contribute to ratio error in a current transformer. This occurs because leakage reactance can cause a phase shift between the primary and secondary currents, leading to an incorrect ratio. Thus, this statement is correct.
2. High Magnetizing Current Increases Phase Angle Error (Statement ii): The magnetizing current is the component of the primary current used for magnetizing the core. A higher magnetizing current results in a greater phase angle error because it enhances the phase displacement between primary and secondary currents. Therefore, this statement is also correct.
3. Burden with Low Power Factor Increases Phase Angle Error (Statement iii): The burden refers to the load connected to the secondary of the transformer. A lower power factor of the burden increases the phase angle error due to the increase in reactive power, which affects the phase relationship. Hence, this statement is correct.
4. Core Saturation Reduces Both Ratio and Phase Angle Errors (Statement iv): Core saturation actually tends to increase errors rather than reduce them. Once the core is saturated, it cannot effectively transfer magnetic flux, leading to both increased ratio and phase angle errors. Thus, this statement is incorrect.

Based on the above analysis, the correct set of statements that cause errors in current transformers is (i), (ii), and (iii) only. Therefore, the correct answer is (i), (ii), and (iii) only.