Select the word you consider most appropriate to fill in the blank space. If I were rich, ______ a lot.

The sentence is a Conditional sentence. When the verb in the if clause is in the past tense, the verb in the main clause is in the conditional tense. The modals will, can are not used in this type of conditional sentence. Similarly, the simple past tense is not used in the main clause. The past tense in the if-clause is not a true past but a subjunctive, which indicates unreality or improbability.