Which describes german engineer charles william siemens's best-known innovation?
a. a device to send wireless signals through the air
b. a process for making steel in a gas furnace
c. the first practical internal combustion engine
d. an instrument to detect icebergs using echoes

Select the five weaknesses of the articles of confederation. congress could not declare war or establish an army. congress could not levy taxes. congress could not control trade. not all the states were represented in congress. no national court system. no executive to enforce the laws. congress could not negotiate with foreign governments. the national government could not borrow money. nine of the states had to agree to pass a law.