How many eruptions did the Kraktau have in total? Also, which years did Krakataus' major eruptions happen in?

1.

The Kraktau had around 50 significant eruptions recorded.

Explanation:

Krakatoa was once a small island of amazing beauty in Indonesia. It was of volcanic origin. The island was destroyed by the 1883 eruption explosion. It is one of the most famous volcanic explosions of all time. Only Rakat part is left of the island.

Eruption list: 1530, 1680-81, 1684, 1883 (Plinian eruption), 1927-30, 1931-32, 1932-34, 1935, 1936, 1937, 1938-40, 1941, 1942, 1943, 1944, 1945, 1946, 1946-47, 1949, 1950, 1952, 1953, 1955, 1958-59, 1959-63, 1965, 1969, 1972-73, 1975, 1978, 1979, 1980, 1981, 1988, 1992-93, 1994-95, 1996, 1997, 1999, 2000, 2001, 2007-8, April 2009-early 2010, Oct 2010 - March 2011, July-Oct 2011, Jan-May, Sep 2012, 2015, 2017, 2018 (22 Dec eruption & tsunami)

2.

The major eruptions in Kraktau happened in the period from May to August 1883.

Explanation:

The dark, angry rumble began to spread from Krakatoe in May 1883. A few months later the rumble became even louder. Ships passing by were reporting explosions that were so loud that their eardrums burst. Just after 10am on August 27, 1883, Krakatoa was blown up by one of the largest explosions ever recorded. The sound of the explosion was heard in Australia, at a distance of 3,500 km. The island collapsed on its own and turned to dust. About 19 cubic miles of volcanic material flew into the air. A cloud of dust rose 80 km uphill and then circled the Earth for years, causing summer temperatures to drop and spectacular sunsets around the world. More than 36,000 people were killed. Anak Krakatau has been the site of frequent eruptions since 1927.

a and b because with the other three, they simplify to something else.