Why is the painting on the China-Russia commemorative cover called Harmonious Beauty? ( )

参考解析：

细节题。A项：艺术家们将象征中俄两国的植物.竹子和桦树画在一起，定位第六段，the work also features bamboos and birch trees, plants symbolic of China and Russia；B项：封面是中国画家徐力和俄罗斯艺术家Vera Laqutenkova共同创作的半身像，只是说明由谁创作，不是原因；C项：这幅画暗示了两国跨越70年的和谐而亲密的关系，定位第五段The painting Harmonious Beauty on the China-Russia commemorative cover, a half-length portrait jointly created by Chinese painter Xu Li and Russian artist Vera Lagutenkova, embodies the close friendship between the two countries spanning seven decades，和谐美象征两国友好的关系；D项：观众可以同时看到一张中国女孩的脸和一张俄罗斯女孩的脸。AD项只是画上有什么，并不是原因。故本题正确答案选C。