Class 12-science

Sir Jis hisab Se aapke maths Mein marks Aaye Chain Us hisab se aapka eligible hona Mushkil Hai Lekin Phir Bhi US college mein admission ke liye cut off par depend karega.

If you have completed your class 12th Science, then there is no procedure to change your subject to commerce. You can directly pursue BBA B.Com (Hons) or any such type of Commerce field.

See, first, do complete your graduation with B.Tech in any field you are interested in. After that, you have to appear for the entrance exams GRE or TOEFL, or IELTS for foreign universities. According to the score in these exams, you can get the admission in aboard for MS course. You can also get scholarship if you scores good. Your B.Tech results will also impact to get admission abroad. Hope this helps you.
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See, you should not go for the diploma or engineering because you have less marks in 12th which will impact bad on your placements. Because almost all companies allow only those students to sit in interview who had minimum 55% marks in 10th and 12th both.
So, you should try for other course.
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No, only students who had PCB in 12th class can go for GNM course. You are not eligible for that.
You should go for other courses like B.Tech, B.Sc, B.C.A, B.Des, etc.
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You should go for BCA or B.Tech with any field in which you are most interested. As you had CS, then you should go for B tech with computer Science branch which is 4 years course. BCA is 3 years degree.
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You should go for B.Tech or BCA course and you can select the field in which you are interested like Mobile technology. You can do your B.Tech in same field. Thanks.

See, if you have maths, then some options are like B.Tech, B.Sc, BCA, B.Des and many more. According to me, you should either go for B.Tech or BCA. If you are from Bio, then you have options like MBBS, BPT, B.Pharma, B.Sc, etc.
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It is really sad to know that you failed in physics. But don't lose hope. There are a no. of career options available to you. But you need to mention your field of interest so that get a rough idea that in which direction you need guidance.

It would be really good if u could give us a hint about your interest. There are a no. of options available to you. But you atleast need to tell your interest and the field that you are interested in.