Name the place in the frog’s body where the blood gives oxygen to the frog’s tissues.

The skin of frogs is literally riddled with blood vessels. The blood vessels are located just under the skin. This allows frogs to breathe while fully immersed in water, as oxygen passes from the water through the skin directly into the blood and carbon dioxide is released.
The answer to the question: the place in the body of the frog, where the blood gives oxygen to the tissues of the frog, is the skin permeated with blood vessels.