In WWI, the was slow and unreliable, but effective.

In WWI, the tank was slow and unreliable, but effective.

Explanation:

As we know WW1 brought many changes when it comes to war efforts. New techniques were introduced and among them usage pf tanks.

Those tanks were heavy and slow, but still practically unbroachable. They were used for the first time in 1916, but until the end of the war were used more frequent.

d.he wanted to send diplomats to communist countries.