2.
看谁算的又对又快。
4 + 1 = {#blank#}1{#/blank#} 3 + 2 = {#blank#}2{#/blank#} 2 + 3 = {#blank#}3{#/blank#}
4 + 2 = {#blank#}4{#/blank#} 3 + 3 = {#blank#}5{#/blank#} 2 + 4 = {#blank#}6{#/blank#}
4 + 3 = {#blank#}7{#/blank#} 3 + 4 = {#blank#}8{#/blank#} 2 + 5 = {#blank#}9{#/blank#}