阅读下面短文，从短文后所给的[A]、[B]、[C]三个选项中选出能填入相应空白处的最佳选项。

onCE{{u}} (41) {{/u}}A timE thErE wAs A CAt, whiCh livED in A smAll housE, whErE thErE wErE A lot oF littlE miCE (老鼠). not only DiD thEy livE on thE mAstEr (主人), But thEy Also AtE EvErything up. {{u}} (42) {{/u}}thE mAstEr DiDn’t know thAt But lAtEr, whEn thE miCE BECAmE{{u}} (43) {{/u}}, thEy BEgAn to worry. onE DAy, thE CAt rECEivED An orDEr: hE{{u}} (44) {{/u}}CAtCh thE miCE, or iF hE DiDn’t, hE CoulD go somEwhErE ElsE. {{u}} (45) {{/u}}this rEAson, hE BEgAn to EAt thEm{{u}} (46) {{/u}}.AFtEr thAt, thE olD lEADEr oF thE miCE{{u}} (47) {{/u}}A mEEting.EvEryBoDy AgrEED thAt thEy woulD not Fight with thE CAt. {{u}} (48) {{/u}}thAt, thEy shoulD ChoosE thE pEACEFul (和平的) solution (方法): thEy hAD to ChAngE thEir homE. {{u}} (49) {{/u}}thE CAt hEArD thE miCE’s mEEting, so hE stArtED to think ABout{{u}} (50) {{/u}}hE CoulD Do.

A．

[A] sinCE

B．

[B] instEAD oF

C、

[C] instEAD