Question

which contributed to the spread of domestic terrorism?
improved methods for recruiting new members
declining economies in various developing countries
civilian unrest due to government - enforced restrictions
colonial groups seeking independence from imperialistic powers

Explanation:

Domestic terrorism often thrives when there is civilian unrest. Government - enforced restrictions can lead to a sense of injustice, marginalization, and anger among the population. This unrest can create an environment where some individuals may be radicalized and turn to domestic terrorist activities.
Improved recruitment methods (while important for terrorist groups) are more of a means rather than a root - cause contributor to the spread. Declining economies in developing countries are more related to issues like poverty and instability in those regions but not directly to domestic terrorism in a general sense. Colonial groups seeking independence is more of an international or anti - imperial struggle rather than a direct cause of domestic terrorism.

Answer:

civilian unrest due to government - enforced restrictions