A randomized controlled trial investigated whether an exercise program increased activity levels in women. Intervention consisted of brief physical activity with regular support that was led by nurses. Control participants received usual care. The order in which participants were allocated to treatment was contained in sequentially numbered opaque envelopes. A researcher not involved in recruitment generated the sequence by computer. Following written informed consent and baseline measurements, treatment allocation was revealed by a nurse not involved in future assessments. Participants were assessed at follow-up by nurses unaware of group allocation; assessors and participants were asked not to discuss group allocation.
Which of the following, if any, are true?
a) Allocation concealment was achieved
b) The trial was single blind
c) The trial was double blind
d) Selection bias was minimized
ECEBM 
a)false because although the order by which participants were allocated to ttt was contained in sequentially numbered opaque envelopes however it was not mentioned whether these envelopes were Sealed or not .
b) & c) are false because type of intervention “physical therapy” can not be “unrevealed” to the participants
d)false because although the samples were randomized, allocation concealment was not achieved
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a) Allocation concealment was achieved by sequentially numbered opaque envelopes
d) Selection bias was minimized by A researcher not involved in recruitment generated the sequence by computer
No blinding where physical activity with regular support that was led by nurses. Control participants received usual care , cant be blinded
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