A) What was the name of the royal physician named as a suspect by many in the Ripper murders ?

B) Which two of Jack the Ripper's victims were found on the same date ?

C) Complete the following quote, made in a letter allegedy written by the killer : "I am down on whores and I shan't quit ripping them ..."

D) What Duke in the British royal family is often named as a potential Ripper suspect ?

Hi Dogspit,
Thanks for your interesting questions.

A) Sir William Withey Gull: Physician to Queen Victoria. Gull shows up as the Ripper in a number of books and films.
Wikipedia

Gull's inclusion in the list of suspects is part of the Royal Conspiracy Theory, which is widely disputed:

Another rumour even claimed Gull was Jack the Ripper, even though by the time of the murders he had had multiple strokes and could barely walk, much less carry out violent murders. Wikipedia

B)Elizabeth Stride and Catherine Eddowes were both murdered on September 30, 1888.
Casebook

C)On the 29th September 1888, the Central News Agency recieved a letter:

Dear Boss, I keep on hearing the police have caught me but they won't fix me just yet...I am down on whores and I shan't quit ripping them till I do get buckled. Grand work the last job was. I gave the lady [ref. to Annie Chapman] no time to squeal. How can they catch me know? I love my work and want to start again. You will soon hear of me and my funny little games... The next job I do I shall clip the lady's ears off and send to the police officers just for jolly...Keep this letter back till I do a bit more work, then give it out straight. My knofe is nice and sharp. I want to get to work right away if I get a chance. Good luck. Yours truly, Jack the Ripper

The letter was considered to be genuine, because only a few hours after the infamous double murder on the 30th of September, the police received a postcard referring to the killings. As details of the murders had not been released, all correspondance up to that date were taken seriously.

"I was not codding [joking], dear old Boss, when I gave you the tip. you'll hear about Saucy Jack's work tomorrow. Double event this time. Number one squealed a bit. Couldn't finish straight off. Had not time to get ears for police. Thanks for keeping last letter back till I got to work again. Jack the Ripper."
Geocities

D)Albert, Duke of Clarence: he was first named as a suspect in 1970 by writer, Thomas Stowell.

Stowell's contention was that the Duke of Clarence had contracted syphilis from a prostitute, gone mad, and in his insanity sought revenge on the class of women that he held responsible for his affliction.
Everything2

Excellent answers and all quite right !

Thanks forthe answers !