A、They get tired of students. B、They are not appreciated by their leaders. C、They feel less valued as a teacher. D、They want to

Almost half of new American teachers leave the profession within five years.[26]Some get tired of large class sizes, limited planning time and support, and wish to feel more valued by society. At the same time, experts say too many teachers lack the required knowledge of what they teach, especially on math and science.
    Criticisms of teaching are usually less about the working conditions than about the pay. A new report calls for an immediate pay increase of fifteen to twenty percent. It says this would lift teachers from the bottom in starting pay among professions.
    The report, "Teachers and the Uncertain American Future", is from the Center lor Innovative Thought. The College Board formed this group last year with "some of the best minds in education", in its words.
    The College Board is a non-profit organization that owns the SAT college entry test. It also administers the Advanced Placement program.
    The report urges new programs to solve a crisis in the number of qualified math and science teachers. It says less than half of the students who finish high school are ready for college-level math or science.
    It says another problem is a shortage of minority teachers, to better represent society.[28]It says two times as many black and three times as many Hispanic, Asian and Native American teachers are needed. The report says the nation needs a new agreement, a "compact", with its teachers to defend its position in the world. All this would be financed with public and private money through a proposed "Teachers’ Trust".
26. Why do many new American teachers give up teaching within five years?
27. What problem does the report aim to solve?
28.How many black teachers are needed according to the report?