be seen to do be seen doing

应选be seen doing
seen是被看见做了某事
所以用doing.

see to
注意，留意；关照

be seen to do (这个比较常用)
被...

如:
1)Travertine tiles are a hard wearing, practical yet timeless floor covering that has to be seen to be appreciated.

2)A large number of mothers who brought their premature babies to a clinic were seen to hold their babies against their right side.

同意be seen doing