Answer the question from the given passage. Your answer should be directly extracted from the passage, and it should be a single entity, name, or number, not a sentence.

Passage: With International Criminal Court trial dates in 2013 for both President Kenyatta and Deputy President William Ruto related to the 2007 election aftermath, US President Barack Obama chose not to visit the country during his mid-2013 African trip. Later in the summer, Kenyatta visited China at the invitation of President Xi Jinping after a stop in Russia and not having visited the United States as president. In July 2015 Obama visited Kenya, as the first American president to visit the country while in office. Question: Who decided not to come visit the country in 2013?
US President Barack Obama

Passage: These chloroplasts, which can be traced back directly to a cyanobacterial ancestor, are known as primary plastids ('plastid' in this context means almost the same thing as chloroplast). All primary chloroplasts belong to one of three chloroplast lineages—the glaucophyte chloroplast lineage, the rhodophyte, or red algal chloroplast lineage, or the chloroplastidan, or green chloroplast lineage. The second two are the largest, and the green chloroplast lineage is the one that contains the land plants. Question: Which lineage includes land plants?
the green chloroplast lineage

Passage: For a precise definition of what it means to solve a problem using a given amount of time and space, a computational model such as the deterministic Turing machine is used. The time required by a deterministic Turing machine M on input x is the total number of state transitions, or steps, the machine makes before it halts and outputs the answer ('yes' or 'no'). A Turing machine M is said to operate within time f(n), if the time required by M on each input of length n is at most f(n). A decision problem A can be solved in time f(n) if there exists a Turing machine operating in time f(n) that solves the problem. Since complexity theory is interested in classifying problems based on their difficulty, one defines sets of problems based on some criteria. For instance, the set of problems solvable within time f(n) on a deterministic Turing machine is then denoted by DTIME(f(n)). Question: What is the most critical resource measured to in assessing the determination of a Turing machine's ability to solve any given set of problems?
time