Complex sentence: The two countries are generally perceived to be on friendly terms, however in recent years there has been growing concern in the PRC over issues such as North Korea's nuclear weapons program, their sinking of the ROKS "Cheonan" and their bombardment of Yeonpyeong.
Split into simpler sentences: The two countries are generally perceived to be on friendly terms. However, in recent years there has been growing concern in the PRC over issues such as North Korea's nuclear weapons program, their sinking of the ROKS "Cheonan" and their bombardment of Yeonpyeong.