下面二叉树的广度优先搜索代码，横线处应填入：
void bfs(TreeNode* root) {
if (root == NULL) return;
queue<TreeNode*> q; q.push(root);
while (!q.empty()) {
________ // 在此处填入代码
cout << node->val << " ";
if (node->left) q.push(node->left);
if (node->right) q.push(node->right);
}
}
- A. TreeNode* node = q.top();
- B. TreeNode* node = q.top(); q.pop();
- C. TreeNode* node = q.front();
- D. TreeNode* node = q.front(); q.pop();
正确答案：D