4. 根据提示，写出可以安排线上视频的提醒。
Janet wants to have a birthday party for grandma. Her cousins are from different cities in the world. They want to have a video call. She has two cousins, Amy and Jim. Her cousin Amy is in Sydney (2 hours ahead of Guangzhou) and Jim is in Tokyo (1 hour ahead of Guangzhou). What is the good time to make a video call?

Tips:
Grandma is usually free at home from 18:00 to 22:00, Guangzhou time. When it is 18:00 in Guangzhou, it is 20:00 in Sydney and it is 19:00 in Tokyo. Do you think it is a good time to make a video call?
If yes, let's help Janet set a time (设定时间) for the video call with her cousins. If no, help Janet find a good

4. (答案不唯一，合理即可) (1) 18:00 (2) is doing homework at home (3) is having dinner at home

【解析】
首先根据时差换算各地时间：悉尼时间比广州快2小时，东京时间比广州快1小时。广州时间18:00时，悉尼为20:00，东京为19:00。若此时Amy在做作业、Jim在吃晚饭，该时间不适合视频通话。需在奶奶空闲的广州时间18:00-22:00内，寻找三方均空闲的时段，比如广州时间19:00时，悉尼21:00，东京20:00，若此时三方都空闲，即为合适时间。
【答案】
(1) 18:00 (2) is doing homework at home (3) is having dinner at home; Yes, 19:00 Guangzhou time（答案不唯一，合理即可）
【知识点】
时区时差计算, 日常时间规划
【点评】
本题以跨时区视频通话为场景，考查时差计算能力与实际问题解决能力，需结合多方时间情况综合判断合适的通话时间，具有较强的实用性。
【难度系数】
0.5