【题目】他很顽固，他一旦下定决心做某些事情，什么都改变不了。
He is very stubborn and once he to do something, nothing can change it.

【答案】has；made；up；his；mind
【解析】make up one's mind下决心，根据句意可知用现在完成时态，所以答案是has made up his mind。