Your child's speech skills have evidently improved. However, they are not perfect as yet and it is absolutely normal. They may still face some difficulty in promtly answering questions or asking them.
When the child enters school it is very clear that he has to interact with people of his age. This interaction at school and other places requires the little one to develop a good speech. You as a mother need to make the child capable of conversing without any hindrance. If you see a problem there, this is what you can do.
What you need to do
There are question/answer sessions at school, which are aimed at increasing the vocabulary and sentence forming ability of the kids. You can practice similar demos at home so that the child can gain confidence to face any type of question. This is very important so that the child can use his brain to start and end a conversation.
Involve other members of the family and start a discussion on any topic. For example- ‘What are the advantages of food?’ Let every member give their own justifications and thoroughly observe the child’s response. Make sure your kid is precise with his words and does not reply in broken sentences. You can also ask the kid to offer his unique question to the other members.
Most kids are shy to interact and end up being weak in language and speech. Question the child whenever you find him free so that he can polish his conversing abilities.