试题题干
Word Formations
Complete the following sentence with the proper form of the word in the bracket.
(valid) This ticket has passed its expiration date, and so it is now 
.
参考答案
试题解析
此处缺少形容词。
根据前面的句子可知，票已经过了有效期了，所以应该是无效了。所以变valid为其反义词invalid。
句意：这张票已经过了有效期，所以现在无效了。