There are multiple imputation methods that can be used for missing data. It comes down to the experience one has using imputation techniques. In most cases, your software by default chooses Listwise deletion. This, of course, all depends on why and how much data is missing. Another approach is imputation which means replacing data values with an estimate, then analyzing the data to see if imputed values were observed.
A question like this is posed to help the hiring manager determine your level of expertise with imputation. First, start with an overview of your knowledge with imputation and imputation techniques. They will probably be looking for something along the lines of mean imputation and single or multiple imputations. The way to answer this question with relation to mean imputation is to talk about Regression Imputation, Hot Deck Imputation, Cold Deck Imputation, Substitution, Stochastic Regression Imputation, and Interpolation and Extrapolation. If a question comes up about single or multiple imputations, it's going to depend on unbiased parameter estimates and accurate standard errors.
