Convert the following active voice sentence into passive voice.
"The United Nations is discussing measures to ensure global peace and stability."
1
Measures to ensure global peace and stability are being discussed by the United Nations.
2
Measures to ensure global peace and stability were discussed by the United Nations.
3
Measures to ensure global peace and stability have been discussed by the United Nations.
4
Measures to ensure global peace and stability was discussing by the United Nations.