In Belgium, it is customary to raise your glass twice when toasting.
Now let's go through each option and explain why it is right or wrong:
A. 1: This option is incorrect because in Belgium, it is customary to raise your glass twice when toasting, not once.
B. 2: This option is correct. In Belgium, it is customary to raise your glass twice when toasting.
C. 3: This option is incorrect because in Belgium, it is customary to raise your glass twice when toasting, not three times.
D. 4: This option is incorrect because in Belgium, it is customary to raise your glass twice when toasting, not four times.
The answer is: B. 2