if only as unless since

Câu hỏi :

In Germany, it's important to be serious in a work situation. They don't mix work and play so you shouldn't make jokes (31) ______ you do in the UK and USA when you first meet people. They work in a very organized way and prefer to do one thing at a time. They don't like interruptions or (32) ______changes of schedule. Punctuality is very important so you should arrive on time for appointments. At meeting, it’s important to follow the agenda and not interrupt (33) ______speaker. If you give a presentation, you should focus (34) ______ facts and technical information and the quality of your company's products. You should also prepare well, as they may ask a lot of questions. Colleagues normally use the family names, and title - for example 'Doctor' or 'Professor', so you shouldn't use first names (35) ______ a person asks you to.