There are three ways you can solve this problem:
1.- You can guide yourself through knowledge, and therefore know the answer. There isn´t much to explain here.
2.- You can eliminate obvious options such as sarcodina or apicomplexa. Euglenoid isn´t an extremely obvious removal since it has a flagela, which can be mistook by a hairy-structure. But, if you do things correctly, obtaining your answer wont be a problem.
3.- You can do an etymologic-guess, which works really well in biology. If you guide yourself this way, you´ll bump into the answer quickly --> "cilio" means hair and according to the description the specimen was covered in hairy structures.
Hope it helped,
BiologiaMagister
