弹簧一物块直线振动系统中，物块质量m，两根弹簧的刚度系数各为<img src="/Image1/4f/4f3dc738d5cdc1dbdf7e79f81ad1b42d.png" />1与<img src="/Image1/4f/4f3dc738d5cdc1dbdf7e79f81ad1b42d.png" />2。若用一根等效弹簧代替这两根弹簧，则其刚度系数<img src="/Image1/4f/4f3dc738d5cdc1dbdf7e79f81ad1b42d.png" />为：（） <img src="/Image1/63/636246c8a8dd8c429a3e58db3bfe2e9b.png" /><br>A:<img src="/Image1/46/460c26351e7f8feb5211848e024ab532.png" /><br>B:<img src="/Image1/6a/6a9ca80cbc992946c5fe9d32a9ee5aca.png" /><br>C:<img src="/Image1/26/2621ba0fac95e9fa51c409ef5907446a.png" /><br>D:<img src="/Image1/4f/4f3dc738d5cdc1dbdf7e79f81ad1b42d.png" />0＝<img src="/Image1/4f/4f3dc738d5cdc1dbdf7e79f81ad1b42d.png" />1+<img src="/Image1/4f/4f3dc738d5cdc1dbdf7e79f81ad1b42d.png" />2