Questão 656755

"Each of these walls must be designed to resist the external forces applied to the wall from earth pressure, surcharge load, water, earthquake etc."

According to the sentence above, one can deduce that

1. designing any retaining wall requires knowledge of lateral earth pressure. 
2. retaining wall design is an iterative method. 
3. it is common for walls to be designed with adequate drainage to prevent water from accumulating behind the wall and producing large additional forces.

Which of the statements is correct?