The instructor demonstrated the correct procedure for pruning a tree.指导者演示了修剪树木的正确步骤。When trees are pruned they bleed sap.修剪树木时会渗出液汁。She's a skillful pruner.她修剪树木很有一手。One of the instructors gave/did a demonstration of how to prune a tree.一位指导者演示了如何修剪树木。