Select the correct passive form of the given sentence.
India and Bhutan signed ten MOUs in the field of space research, aviation, power and education.

Ten MOUs in the field of space research, aviation, power and education have been signed by India and Bhutan.

Ten MOUs in the field of space research, aviation, power and education will be signed by India and Bhutan.

Ten MOUs in the field of space research, aviation, power and education were signed by India and Bhutan.

Ten MOUs in the field of space research, aviation, power and education are being signed by India and Bhutan.