The question told us that f(t) has removale point when t=1,2,3,4…. and the general function discontinuous. However, back to the definition of integrade, its general idea is about divide part of a function into infinitely pieces and add those all together by select a certain point on the width you choose; thinking of this, we can apply that idea into this question, which we can choose that certain point ti without endpoints defined. Therefore, we can say that it is integrable.