Pass, both are very good!

Eric and Shin Min Ah
Sorry but...fail

Kim Rae Won and Park Shin Hye
Pass.. though I dropped Doctors, I thought they had a good chemistry. :)

Park Bo Young and Song Joong Ki (this is my dream. ^^Them in a drama together.)
Pass... I'm sure they would make a good pair!

Ryu Joon Yeol and Park Bo Young
Pass. I think they would be a cute couple ^^

Ha Ji Won and Lee Joon Gi
fail... I do not like Ha Ji Won!

Moon Chae Won and Lee Joon Gi
Pass
Jung Kyung Ho and Moon Chae Won
Pass, I can see that. 

Park Bo Gum and Kim Ji Won 
Pass, both are adorable!

Lee Kwang Soo and Kim Seul Gi
Pass sure make a funny couple
Lee Jong Suk and Han Groo
Pass, that would be a cute pairing to see in a drama. 

Sung Hoon and Seo Hyun Jin
Pass I can imagine the hot chemistry
Yoon Hyun Min and Nam Gyu Ri
Pass. They would be great couple, especially in an action drama :)

Ji Chang Wook and Park Bo Young
Pass. I could see it. 

Yoo In Na & Ji Chang Wook
Pass

Miura Shohei and Kiritani Mirei