It is easier
| P : | to venture into space |
| Q : | for men |
| R : | beneath their feet |
| S : | than to explore |
QRPS
QPSR
PSRQ
PQSR
Next Question
The appearance | P : | this dinosaurs were at their peak |
| Q : | of the first mammals on the earth |
| R : | at the time when |
| S : | went almost unnoticed |