recently/ UN committee/ report/ world/ oil and gas supplies/ last/ about 100 years/ if/ use/ carefully//

A. Recently UN committee reported that world's oil and gas supplies, will last about 100 years if they are used carefully.

B. Recently the UN committee reported that the world's oil and gas supplies would last about 100 years if using carefully.

C. Recently a UN committee reported that the world's oil and gas supplies would last about 100 years if used carefully.

D. Recently a UN committee reported that the world's oil and gas supplies would last about 100 years if it was used carefully.