フリー問題

問題文

Which wildcard characters may an enterprise dial pattern carry, and what restriction does the guidance place on the one standing for a run of digits?

選択肢

1. It may carry the exclamation mark alone, since a pattern that has to reach a single digit is written out with the digit itself rather than with X standing in for it, and there is no rule about where the mark sits.
2. It may carry X for a single digit, the exclamation mark for a run of them, and the question mark for a digit that may be left out, with the marks free to sit anywhere and the only rule being that a pattern opens with a digit.
3. It may carry either X or the exclamation mark anywhere in the string, and the two of them may be combined in one pattern as long as the only wildcard at the end is the one standing for a run.
4. It may carry X for a single digit and the exclamation mark for a run of them, with the exclamation mark allowed just once at the end and only inside a pattern written in the international format for numbers.