Describe a situation that others didn't tell you the whole truth.
You should say:
what the situation was
who was involved
why they didn't tell you the whole truth
and explain how you felt when you found out you were not told the whole truth.
Well, actually there were many times when I was not told the whole truth. But the one that impressed me most, I must say, would be the unforgettable birthday party I spent last year. That was a Tuesday, if I remember it right. I got up early and caught the bus to go to work as usual, because I almost forgot the birthday thing.
My mom told me that she would not be at home that night and I must cook the dinner for myself. But after working for the whole day, I got home almost exhausted and I just wanted to have a good rest. But when I opened my room door and turned on the light, I was shocked by what I saw in front of me.
The whole room was decorated into warm pink, with some colorful balloons hanging on the wall. While I was standing there stunned with my mouth open, my parents and my younger sister started to sing the birthday song for me behind a well-prepared dinner among which there was a big cake. What a pleasant surprise!
At that moment, I could not say a word but let the tears stream down my face. All my tiredness had gone away, and I felt I was the happiest person in the world.