Here are my solutions:

1. Dennis : C :: Bjarne : ?

   C++

2. Sa: C :: Pa : ?

   I believe this has something to do with music. I know "Sa" and "Pa" mean something in music and have heard about C minor. But I have no knowledge of music.

3. 6 : C :: 53 : ?

   I

4. 100 : C :: 500 : ?

   D

5. 50 : C :: 122 : ?

   F

I'll add a couple more:

1. 195 : C :: 209 : ?
2. Bohai : C :: Oolong : ?

Prasanna,

Bohai : C :: Oolong : T (Bohai sea and Oolong tea).

Sa : C :: Pa : G

195 : C :: 209 : J (EBCDIC)

That was fun!

1 : C :: 4184 : ?

Aby,

1 : C :: 4184 : J (1 Cal = 4184 joules)