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:
| Nation | Birth date | Height (m) | Weight (kg) | World Rank |
| --- | --- | --- | --- | --- |
| Australia (AUS) | 1958-04-14 | 1.83 | 110 | 9 |
| Australia (AUS) | 1967-01-26 | 1.93 | 96 | 9 |
| Austria (AUT) | 1965-03-01 | 1.80 | 90 | – |
| Austria (AUT) | 1976-05-26 | 1.90 | 108 | – |
| Brazil (BRA) | 1973-04-15 | 1.88 | 78 | 6 |
| Brazil (BRA) | 1971-07-31 | 1.85 | 100 | 6 |
| China (CHN) | 1969-09-29 | 1.85 | 85 | – |
| China (CHN) | 1988-11-09 | 1.90 | 100 | – |
| Croatia (CRO) | 1973-06-16 | 1.86 | 100 | 11 |
| Croatia (CRO) | 1983-10-16 | 1.75 | 100 | 11 |
| France (FRA) | 1968-07-01 | 1.88 | 100 | 8 |
| France (FRA) | 1972-04-14 | 1.94 | 100 | 8 |
| Great Britain (GBR) | 1976-03-21 | 1.85 | 92 | 12 |
| Great Britain (GBR) | 1976-12-17 | 1.85 | 104 | 12 |
| Germany (GER) | 1971-12-12 | 1.96 | 102 | 10 |
| Germany (GER) | 1971-10-02 | 1.85 | 83 | 10 |
| Ireland (IRL) | 1983-03-29 | 1.88 | 88 | 48 |
| Ireland (IRL) | 1985-07-25 | 1.90 | 105 | 48 |
| Italy (ITA) | 1971-04-16 | 1.82 | 92 | 4 |
| Italy (ITA) | 1978-11-05 | 1.94 | 103 | 4 |
| New Zealand (NZL) | 1971-05-13 | 1.76 | 82 | 5 |
| New Zealand (NZL) | 1981-06-09 | 1.95 | 110 | 5 |
| Poland (POL) | 1975-04-29 | 1.93 | 100 | 1 |
| Poland (POL) | 1974-02-15 | — | — | 1 |
| Portugal (POR) | 1969-07-29 | 1.74 | 83 | 7 |
| Portugal (POR) | 1980-07-17 | 1.92 | 112 | 7 |
| Switzerland (SUI) | 1978-02-07 | 1.91 | 100 | 2 |
| Switzerland (SUI) | 1976-12-20 | 1.90 | 99 | 2 |
| Sweden (SWE) | 1969-12-13 | 1.90 | 97 | 3 |
| Sweden (SWE) | 1981-01-16 | 1.81 | 102 | 3 |
| United States (USA) | 1950-07-15 | 1.91 | 99 | 17 |
| United States (USA) | 1978-05-11 | 1.85 | 102 | 17 |
Question:
what is the nation when the world rank is 6 and the birth date is 1971-07-31?
Answer:
Brazil (BRA)