A - has moved [present perfect] The action occurred during the period from 1911 until now. The past perfect applies to an ongoing state, repeated action, or action that occurred during a period that extends to the present. --- Other choices B - was moved [simple past - passive voice] Passive voice doesn’t apply here. C - was moving [past continous] This fits a time or time period that does not extend to the present. For example: Measurements in 1911 and 1912 showed that the tower was moving at ... D - had moved [past perfect] This applies to the earlier of two actions or states in the past. Examples: Measurements in 1912 showed the tower had moved ... since 1911. ---- Other comments I think the test is missing the best answer "has been moving” [present perfect continous]. The present perfect continuous applies to an ongoing action which is incomplete at the present moment. Examples: The sun has been shining all morning [and it will continue]. Since 1911, the tower has been moving at 1.2 mm per year. If the question were phrased as “ ___ 1.2 mm each year,” then the perspective is a series of repeated actions and “ has moved 1.2 mm each year” is natural (in my opinion). Howevr, the question was phrased as “ __ 1.2 mm per year,” which gives the perspective of an ongoing action and “ has been moving 1.2 mm per year” is best (in my opinion). Additionally, North Americans generally substitute the simple past for the present perfect and so we would usually says “moved 1.2 mm per year” or “ was moving 1.2 mm per year."

was moving потому что per year

has moved