Mid term revision ( Perfect structures and tenses)

I started discussing my research proposal with my professor at the beginning of my course. We're still dicussing it

Nam's still studying English.He started studying it two years ago

I started learning how to play the piano eight months ago. I'm still learning it.

He attended two online vocational courses: one in 2012 and the other in 2013. (twice)

They visited this college in 2009, 2012 and 2014. (three times)

In the Tree Planting Competition, the students in Group 11G planted the most trees in the schoolyard. They were praised for that.

After she replaced all the light bulbs in her house with LED lights, she saved a lot of money on her electricity bills.

Sam had not worked hard enough in his previous job. He regretted it.

Someone had cut down the oldest tree in the park. The police suspected Mike of doing it.

 Since the farmers used too much chemical fertilizers on their farm, they now have to drink polluted water.