The customs and laws relating to the aspects of the people's life must be understood in order to master the culture and language of that people. The traveler in strange lands is expected to respect the customs as well as to obey the laws.The author advises us _______.
选项：

A:to make hay while the sun shines;
B:to do as the Romans do when in Rome;
C:to make both ends meet in our daily life;
D:not to do to others what you would not have others do to you