这些副词或词组均有“肯定地，当然”之意。
certainly : 用于肯定的答复或强调有把握、深信不疑。
- She certainly had a friend called Mark, but I don't know whether he was her boyfriend.
她确实有个朋友叫马克，不过我不知道他是不是她男友。 - "This is rather a difficult question." "Yes, it's certainly not easy."
“这实在是个难题。”“是呀，确实不容易。” - "Do you think more money should be given to education?" "Certainly!"
“你认为应当给教育拨更多经费吗?”“当然啦！” - "Had you forgotten about our anniversary?" "Certainly not! I've reserved a table at Michel's restaurant for this evening."
“你是不是把我们的结婚纪念日给忘了?”“当然没有！我已经在米歇尔餐厅预订了今晚的桌位。”
naturally : 指自然而然，毫无造作或天生如此。
- A healthy body will be able to fight off the illness naturally without the use of medicine.
健康的身体无需药物，自身便能抵御疾病。
of course : 指毫无疑问，自然如此。可与certainly和naturally换用。
- "Can you help me?" "Of course."
“你能帮帮我吗？”“当然可以。” - "May I look at your newspaper?" "Of course you can."
“我能看看你的报纸吗？”“当然可以。” - "Have you written your English essay yet?" "Of course, I finished it last week."
“你的英语论文写了吗？”“当然了，我上周就写完了。”
surely : 表一种必然的可能性，也可表示信心或不轻信。强调主观判断。
- The problem surely lies in the design of the equipment.
问题肯定出在设备的设计上。 - "May I sit here?" "Surely." (= Yes, certainly.)
“我能坐在这里吗?”“当然可以。” - Without more food and medical supplies, these people will surely not survive.
如果没有更多的食品和医疗物资，这些人肯定活不下去。
