Fill in the blanks with the appropriate form of the verbs given in brackets:
Linguists___(suggest/suggests) that speech milestones___(is/are) reached in a fixed sequence and at a constant age, but there___(is/are) cases where speech ___(has/have) started late in a child who eventually___(turn/turns) out to be of high IQ. At twelve weeks a baby___(smile/smiles) and___(utter/utters) vowel-like sounds; at twelve months he can speak simple words and understand simple commands; at eighteen months he___(has/have) a vocabulary of three to fifty words. At three he___(know/knows) about 1000 words which he can put into sentences, and at four his language___(differ/differs) from that of his parents in style rather than grammar.



Suggest,are,are,have,turns,smiles,utters,has, knows,differs