The text below has incomplete sentences. Choose the one word or phrase from each number that best completes the sentences.

    Children (41) ____ linguistic milestones in parallel fashion, regardless of the special language they are exposed to. For example, at about 6-8 months all children start to babble, that is, to (42) ____ like bababa. At about 10-12 months they (43) ____ their first words, and between 20 and 24 months they begin to put words together. It (44) ____ that children between 2 and 3 years speaking (45) ____ use infinitive verbs in main clauses or omit sentential subjects, although the language they are exposed to may not have this option.

    Across languages young children also over-regularize the past tense or other tenses of irregular verbs. Interestingly, similarities in language acquisition are (46) ____ not only across spoken languages, but also between (47) ____. For example, at the age when hearing babies start to babble orally, deaf babies start to do the same (48) ____. It (49) ____ that the timing and milestones of language acquisition are so similar and that the content of early languages is virtually identical, despite great variations in input and in (50) ____.

(Taken from Guasti, Maria T. 2002. Language Acquisition: The Growth of Grammar. London: The MITT Press, p. 4.)

(49) ....