Please read the following table in Markdown format and then answer the question according to the table. Table cells in one row are seperated by '|', and different rows are seperated by '
'.

Table:
| Date | Round | Opponent | Venue | Result | Attendance |
| --- | --- | --- | --- | --- | --- |
| 16 September 1970 | R1 | Aris Salonika | A | 1-1 | 50000.0 |
| 30 September 1970 | R1 | Aris Salonika | H | 5-1 | 40425.0 |
| 21 October 1970 | R2 | CSKA Sofia | A | 1-0 | 45000.0 |
| 4 November 1970 | R2 | CSKA Sofia | H | 1-0 | 41613.0 |
| 10 March 1971 | QF | Club Brugge | A | 0-2 | 23000.0 |
| 24 March 1971 | QF | Club Brugge | H | 4-0 ( a.e.t. ) | 45558.0 |
| 14 April 1971 | SF | Manchester City | H | 1-0 | 45595.0 |
| 28 April 1971 | SF | Manchester City | A | 1-0 | 43663.0 |
| 19 May 1971 | F | Real Madrid | N | 1-1 ( a.e.t. ) | 45000.0 |
| 21 May 1971 | F | Real Madrid | N | 2-1 | 24000.0 |
Question:
What is the round for the opponent CSKA Sofia in Venue A?
Answer:
R2