Select the phrase/connector from the given three options which can be used to form a single sentence from the two sentences given below, implying the same as expressed in the statement sentences.
Converting organic waste to fuel was not economically feasible. It required very high temperatures and energy.
1. because
2. certainly
3. economically feasible
1
Only 1
2
Only 2
3
Only 3
4
Both 1 and 3
5
None of these