Which of the following are true of the spanish exploration and conquests in america?
they followed the mississippi from its source to its mouth.
they claimed large stretches of land in the southern u. s.
they claimed the st. lawrence river.
spain gained great wealth.

i can choose more than !

WRONG - They followed the Mississippi from its source to its mouth. 
WHY - Spanish Conquistador Hernando de Soto discovered the river whilst in the south of the US he died of fever on the west bank near to the delta. The source of the Mississippi is Lake Itasca in Minnesota (north US near to Canada, the spanish didn't get this far north for a long time afterwards). 

TRUE - They claimed large stretches of land in the southern US 
WHY - open plains inhabited by simple natives means easy conquest for Spain, they grabbed all the land they could like any other country would at the time. In fact at the peak of spanish colonisation they had claimed most of of N America. 

FALSE - They claimed the St. Lawrence River 
WHY - The Spanish never conquered NE America the english and french got there first and fought over it as a strategic point. 

TRUE - Spain gained great wealth 
WHY - The spanish sniffed out riches wherever they went they are historically famous for grabbing all the gold they can get. Most of the early conquests were funded by the spanish royal family so that is where the profits were eventually directed.

hopefully this helps