All employees in D wing were given the morning

【問題】
All employees in D wing were given the morning off while technicians ________ the new power lines.

【選択肢】
1.　were installing
http://jibun.atmarkit.co.jp/scenter/ittrain/93_20060927_a1.html

2.　install
http://jibun.atmarkit.co.jp/scenter/ittrain/93_20060927_a2.html

3.　had installed
http://jibun.atmarkit.co.jp/scenter/ittrain/93_20060927_a3.html

4.　are installing
http://jibun.atmarkit.co.jp/scenter/ittrain/93_20060927_a4.html

問題提供：リアル・イングリッシュ・ブロードバンド株式会社
http://jibun.atmarkit.co.jp/misc/ct.php?id=TR56_RE1
No.09320060927