@ keith williams
I am sorry. I learn faster by absorbing the correct answer. 
If there is any queries about the answer chosen, I will raise it.
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Q7. Water injection is used for take-off:
(c) only at high altitude airfields where the prevailing temperature is high
(d) at airfields with an ambient temperature above 30F.
Either (c) or (d), still unsure
HazelNuts39 provided answer with "(b) to cool the turbine blades". Hum... 
Q8. In a high ratio by-pass engine
(b) not all the air go thru the high poressure compressor
(c) not all the air go thru low pressure compressor
Either (b) or (c), still unsure