360. At times, a longer and shorter form of the same text is given. In choosing between these two forms, a pastoral criterion should be kept in mind. On such an occasion, attention should be paid to the capacity of the faithful to listen with fruit to a reading of greater or lesser length, and to their capacity to hear a more complete text, which is then explained in the Homily.[General Introduction to the Lectionary (GILM) 80]
The ability to “hear” a text is more affected by the person proclaiming it–how it is presented–rather than its length. That said, the options given are sometimes useful.
361. When a possibility is given of choosing between one or other text laid down, or suggested as optional, attention shall be paid to the good of participants, whether, that is to say, it is a matter of using an easier text or one more appropriate for a given gathering, or of repeating or setting aside a text that is assigned as proper to some particular celebration while being optional for another,[GILM 81] just as pastoral advantage may suggest.
Such a situation may arise either when the same text would have to be read again within a few days, as, for example, on a Sunday and on a subsequent weekday, or when it is feared that a certain text might give rise to some difficulties for a particular group of the Christian faithful. However, care should be taken that, when choosing scriptural passages, parts of Sacred Scripture are not permanently excluded.
362. The adaptations to the Ordo Lectionum Missae as contained in the Lectionary for Mass for use in the Dioceses of the United States of America should be carefully observed.
And if you would like, you can consult the GILM, which we covered on these pages last year at this time.