Question

1. typically, the ice sheet begins to show evidence of thawing in late summer, following several weeks of higher temperatures. ______ in the summer of 2012, virtually the entire greenland ice sheet underwent thawing at or near its surface by mid - july, the earliest date on record.

a) for example,
b) however,
c) as such,
d) moreover,

Explanation:

The first sentence describes the typical time (late summer) for the ice sheet to thaw. The second sentence talks about 2012 when the thawing happened much earlier (mid - July). This shows a contrast between the typical situation and the 2012 situation. "For example" is used for giving examples, "As such" is used for showing a result, "Moreover" is used for adding information. "However" is used for showing a contrast, so it fits here.

Answer:

B) However,