Question

both state and federal government have the power to
make treaties and collect taxes.
build roads and make treaties.
build roads and enforce laws.
make treaties and declare war.

Explanation:

Making treaties and declaring war are exclusive federal - powers. Collecting taxes is a power of both state and federal governments, and building roads is also a power that both can have. Enforcing laws is also a shared power in some contexts. The power to make treaties is mainly a federal power. So, the power to build roads and enforce laws is a power that both state and federal governments can have.

Answer:

build roads and enforce laws.