Which of these is a complex sentence?

Immigrants who came to work in factories lived in urban neighborhoods.

"Old" immigrants often settled on farms, but most "new" ones lived in cities.

In the past, many immigrants had come from northern and western Europe.

Immigrants working long hours and facing crowded living conditions.

Require the nobles and clergy to pay taxes.

Idon't know the answer is

In 911, a group of vikings lead by rollo besieged paris and chartres. after a victory near chartres on 26 august, charles decided to negotiate with rollo. the talks were led by hervé, the archbishop of reims. this resulted in the treaty of saint-clair-sur-epte, which granted rollo and his soldiers all the land between the river epte and the sea. it also granted him brittany, "for his livelihood". at the time, brittany was an independent land which france had not been able to conquer. in exchange, rollo promised the king his loyalty and military assistance when needed. also rollo also agreed to be baptised and to marry gisela, the king's daughter. the territory given rollo is about the same as upper normandy.