LTE offers higher peak data transfer rates -- up to 100 Mbps downstream and 30 Mbps upstream. It also provides reduced latency, scalable bandwidth capacity and backward-compatibility with existing GSM and UMTS technology. Future developments could yield peak throughput on the order of 300 Mbps.
Various telephone companies launched LTE at different times in different countries. Some European countries adopted the standard as early as 2009, while North American countries adopted it in 2010 and 2011. As of this writing, South Korea has the best LTE penetration with 97.5% of the country covered by LTE service. The U.S. has 90.3% LTE penetration.
LTE Advanced (LTE-A), which was meant to improve the current standard, was first tested in 2011 in Spain. LTE-A improves upon the radio technology and architecture of LTE. LTE-A has been tested to show that the download and upload speeds are around two to three times faster than standard LTE. 3GPP made sure that all LTE-A devices would be backward-compatible with standard LTE.

 From the paragraph above, what is the maximum uplink rate that LTE can provide? （ ）.

Some European countries adopted the standard as early as （ ）.

 As of this writing, （   ） has the best LTE penetration.

 What are the improvements of LTE-A? （   ）.