please help me , select from 2 table with a function column

Question

hello every one 

 

I have 2 table

1-id,name,family

2-id,score 

and want to select command below but sql server take me error 

 

select member.id,member.name,member.family,sum(activity.score) from member inner join activity on member.id=activity.mem_id

and error 

 

Msg 8120, Level 16, State 1, Line 1

Column 'member.id' is invalid in the select list because it is not contained in either an aggregate function or the GROUP BY clause.

please help me

I am in trouble