Indexes are used to make searches faster - so dropping an index may slow some seek operations and leave others unchanged.
An index is NOT required to maintain a foreign key - however it is often benificial.
Indexes use additional disk space - so dropping an index should release disk space.
Indexes must be maintained when inserting a record. If an index is dropped then the insertion should be faster.
In most cases updates will be faster with fewer indices.
There may be instances where an update involves a seek - in such cases the update may be slower. There is a better answer than this.
The option of dropping a secondary index to a table is being considered. Which of the following is most likely to be a consequence of dropping the index?