
Option (a) Some fruits are lemon: Here, some lemons are oranges and all oranges are fruits. Thus, some lemons are fruits. So, option (a) follows.
Option (b) Some oranges are not sweet: Some oranges which are lemon are not sweet. So, option (b) follows.
Option (c) Some oranges are vegetables is a possibility: here, all oranges are fruits and some fruits are vegetables. So, some oranges are vegetables is a possibility. So, option (c) follows.
Option (d) No vegetable is sweet is a possibility: Here, some fruits are vegetables and some fruits are not sweet. So, there is a possibility that no vegetable is sweet. So, option (d) follows.