DDR-:Double Data Rate,
SDR-:single Data rate,DDR transfers data twice the speed of
SDR.

DDR is double data rate...
SDRAM is synchronized dynamic Ram....

the difference between both is how the data is stored and 
transferred by them.

SDRAM stands for Synchronous Dynamic Random Access Memory
DDR-SDRAM stands for Double Data Rate Synchronous Dynamic
Random Access Memory

The difference between SDRAM and DDR is that SDRAM transfers
data on the rising edge of the clock signal. However, DDR
transfers data on both the edges of the clock signal ie., on
the rising and the falling edges of the clock signal. As a
result, the data transfer rate of DDR is faster than SDRAM.
It is almost twice the speed of the SDRAM.

answer 1 sdram - single data rate is incorrect

it is  synchronous dynamic random access memory 

answer 2 is correct

and ddr - double data rate

SD-RAM

1)Minimum storage capacity of is 32 MB  MAX  512 MB

2)The minimum data transfer speed or frequency 66 MHZ and
max 166 MHZ

3)The pin no is 128

4)Storage capacity and frequency is less

5)Synchronous Dynamic Random Access Memory 


DDR- RAM

1)Minimum storage capacity of is 64 MB  MAX  1GB onwards

2)The minimum data transfer speed or frequency 200MHZ and
max 667 MHZ

3)The pin no is 168,172,184,192

4)Storage capacity and frequency is more

5)Double Data Rate Random Access Memory