| a. In every situation, the data generating mechanism can create predictors that only have a single unique value |
| b. Predictors might have only a handful of unique values that occur with very low frequencies |
| c. The function findLinearCombos uses the QR decomposition of a matrix to enumerate sets of linear combinations |
| d. All of the mentioned |
| Answer: In every situation, the data generating mechanism can create predictors that only have a single unique value |