Ans. is 'b' i.e., 10 words * Although a child has a vocabulary of 250 words at 3 years, the child can use sentence of 10 words at 5 years.* At 18 months, the child can use 10 words with meaning.Other milestones asked in the question are achieved in children older than 18 months* Making a tower of 9 cubes - 30 months* Turn pages of book one at a time - 2 years* Ride tricycle - 3 yearsMilestones achieved at 18 months of age* Starts running (runs stiffy)* Can feed himself from a cup.* Can use 10 words with meaning.* Name pictures* Builds tower of 4 cubes.* Ready for starting toilet training.* Copies parents in task.